Q 1MathematicsSection A • MCQcomplex numbers+2 / -0If 𝛼 and 𝛽 are the roots of the equation 𝑥2+𝑥+1=0 then 𝛼2026+𝛽2026=−1Incorrect0Incorrect1Incorrect2IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (A)Step-by-Step Solution:Since 𝛼 and 𝛽 are roots of 𝑥2+𝑥+1=0 we know that 𝑥3−1=(𝑥−1)(𝑥2+𝑥+1) So the roots of 𝑥2+𝑥+1=0 satisfy 𝛼3=1,𝛽3=1 Also, from the quadratic equation, 𝛼+𝛽=−11=−1 Now, 2026=3×675+1 So, 𝛼2026=𝛼3×675+1=(𝛼3)675𝛼=1675𝛼=𝛼 Similarly, 𝛽2026=𝛽 Hence, 𝛼2026+𝛽2026=𝛼+𝛽=−1 So the correct option is −1 Option A.
Q 2MathematicsSection A • MCQpermutations and combinations+2 / -0The number of ways that 8 beads of different colours can be strung to form a necklace is5040Incorrect2520Incorrect2840Incorrect5080IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (B)Step-by-Step Solution:For 8 beads of different colours, first arrange them in a circle. In a circular arrangement, rotations are considered the same. So the number of circular arrangements of 8 different beads is (8−1)!=7! 7!=5040 But in a necklace, we can turn it over. So a clockwise arrangement and its anticlockwise arrangement are also considered the same. Hence, we divide by 2: 7!2=50402=2520 So, the number of ways is 2520 Correct option: Option B.
Q 3MathematicsSection A • MCQproperties of triangles+2 / -0In Δ𝐴𝐵𝐶, if ∠𝐴=90∘, then sin(𝐵−𝐶)=𝑎2−𝑐2𝑎2+𝑐2Incorrect𝑐2−𝑎2𝑐2+𝑎2Incorrect𝑏2−𝑐2𝑏2+𝑐2Incorrect𝑐2−𝑏2𝑐2+𝑏2IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (C)Step-by-Step Solution:In Δ𝐴𝐵𝐶, sides 𝑎,𝑏,𝑐 are opposite to angles 𝐴,𝐵,𝐶 respectively. Given, ∠𝐴=90∘ So 𝐵𝐶=𝑎 is the hypotenuse, and 𝑏,𝑐 are the other two sides. Since 𝐵+𝐶=90∘ we need to find: sin(𝐵−𝐶) Using the identity, sin(𝐵−𝐶)=sin𝐵cos𝐶−cos𝐵sin𝐶 In the right triangle, sin𝐵=𝑏𝑎,cos𝐵=𝑐𝑎 and sin𝐶=𝑐𝑎,cos𝐶=𝑏𝑎 So, sin(𝐵−𝐶)=𝑏𝑎⋅𝑏𝑎−𝑐𝑎⋅𝑐𝑎 sin(𝐵−𝐶)=𝑏2−𝑐2𝑎2 By Pythagoras theorem, 𝑎2=𝑏2+𝑐2 Hence, sin(𝐵−𝐶)=𝑏2−𝑐2𝑏2+𝑐2 So the correct option is: Option C 𝑏2−𝑐2𝑏2+𝑐2
Q 4MathematicsSection A • MCQtrigonometric ratios and identities+2 / -0The value of cos210∘−cos10∘cos50∘+cos250∘ is equal to....14Incorrect12Incorrect34Incorrect1IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (C)Step-by-Step Solution:Take 𝐸=cos210∘−cos10∘cos50∘+cos250∘ Use the identities: cos2𝐴+cos2𝐵=1+cos(𝐴+𝐵)cos(𝐴−𝐵) and cos𝐴cos𝐵=12{cos(𝐴+𝐵)+cos(𝐴−𝐵)} Here 𝐴=10∘ and 𝐵=50∘. So, cos210∘+cos250∘=1+cos60∘cos40∘ Since cos60∘=12, cos210∘+cos250∘=1+12cos40∘ Also, cos10∘cos50∘=12{cos60∘+cos40∘} =12{12+cos40∘} =14+12cos40∘ Now substitute: 𝐸=1+12cos40∘−(14+12cos40∘) 𝐸=1−14 𝐸=34 So the correct option is 34 Option C.
Q 5MathematicsSection A • MCQtrigonometric equations+2 / -0The general solution of cos4𝜃=cos3𝜃 is 𝜃=.....2𝑛𝜋7,𝑛∈𝑍Incorrect2𝑛𝜋5,𝑛∈𝑍Incorrect𝑛𝜋,𝑛∈𝑍Incorrect4𝑛𝜋3,𝑛∈𝑍IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (A)Step-by-Step Solution:We need to solve cos4𝜃=cos3𝜃 Using the NCERT result: cos𝐴=cos𝐵⟹𝐴=2𝑛𝜋±𝐵,𝑛∈𝑍 Here, 𝐴=4𝜃,𝐵=3𝜃 So, 4𝜃=2𝑛𝜋±3𝜃 Now take both cases. For the positive sign: 4𝜃=2𝑛𝜋+3𝜃 𝜃=2𝑛𝜋 For the negative sign: 4𝜃=2𝑛𝜋−3𝜃 7𝜃=2𝑛𝜋 𝜃=2𝑛𝜋7 The values 𝜃=2𝑛𝜋 are already included in 𝜃=2𝑛𝜋7 when 𝑛 is a multiple of 7. So the general solution is 𝜃=2𝑛𝜋7,𝑛∈𝑍 Correct option: A
Q 6MathematicsSection A • MCQstraight lines and pair of straight lines+2 / -0The line 2𝑥+𝑦=4 intersects X and Y axes at points A and B respectively. Let 𝐶(𝑝,𝑞) be the point such that the lines AC and BC are perpendicular. The distance of point C from the midpoint of segment AB is...√2Incorrect√5Incorrect2√2Incorrect2√5IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (B)Step-by-Step Solution:The line is 2𝑥+𝑦=4 It meets the 𝑋-axis where 𝑦=0. 2𝑥+0=4⇒𝑥=2 So, 𝐴=(2,0) It meets the 𝑌-axis where 𝑥=0. 0+𝑦=4⇒𝑦=4 So, 𝐵=(0,4) Now 𝐴𝐶 and 𝐵𝐶 are perpendicular, so ∠𝐴𝐶𝐵=90∘ This means 𝐶 lies on the circle having 𝐴𝐵 as diameter. By the circle theorem, angle in a semicircle is a right angle. So the distance of 𝐶 from the midpoint of 𝐴𝐵 is the radius of this circle. First find the length of 𝐴𝐵: 𝐴𝐵=√(2−0)2+(0−4)2 𝐴𝐵=√4+16 𝐴𝐵=√20=2√5 Radius =𝐴𝐵2 Distance of 𝐶 from midpoint of 𝐴𝐵=2√52=√5 So the correct option is √5 Option B.
Q 7MathematicsSection A • MCQstraight lines and pair of straight lines+2 / -0If the distance between the lines represented by (𝑥−2𝑦)2+𝑘(𝑥−2𝑦)=0 is 3 units and 𝑘>0 then the equations of the lines are𝑥−2𝑦=0 and 𝑥−2𝑦+√3=0.Incorrect𝑥−2𝑦=0 and 𝑥−2𝑦+√5=0.Incorrect𝑥−2𝑦=0 and 𝑥−2𝑦+3√3=0.Incorrect𝑥−2𝑦=0 and 𝑥−2𝑦+3√5=0.IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (D)Step-by-Step Solution:The given equation is (𝑥−2𝑦)2+𝑘(𝑥−2𝑦)=0 Take (𝑥−2𝑦) common: (𝑥−2𝑦)[(𝑥−2𝑦)+𝑘]=0 So the two lines are 𝑥−2𝑦=0 and 𝑥−2𝑦+𝑘=0 These are parallel lines because both have the same coefficients of 𝑥 and 𝑦. The distance between two parallel lines 𝑎𝑥+𝑏𝑦+𝑐1=0 and 𝑎𝑥+𝑏𝑦+𝑐2=0 is |𝑐1−𝑐2|√𝑎2+𝑏2 Here, 𝑥−2𝑦=0 and 𝑥−2𝑦+𝑘=0 So 𝑎=1, 𝑏=−2, 𝑐1=0, and 𝑐2=𝑘. Given distance is 3 units: |𝑘−0|√12+(−2)2=3 𝑘√5=3 since 𝑘>0. So, 𝑘=3√5 Hence the equations of the lines are 𝑥−2𝑦=0 and 𝑥−2𝑦+3√5=0 So the correct option is Option D
Q 8MathematicsSection A • MCQstraight lines and pair of straight lines+2 / -0If the slope of one of the two lines given by 𝑥2𝑎+2𝑥𝑦ℎ+𝑦2𝑏=0 is twice that of the other, then ℎ2:𝑎𝑏= ...1:2Incorrect2:1Incorrect8:9Incorrect9:8IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (C)Step-by-Step Solution:For the pair of straight lines, 𝑥2𝑎+2𝑥𝑦ℎ+𝑦2𝑏=0 both lines pass through the origin. So if the slope of a line is 𝑚, then we put 𝑦=𝑚𝑥 Substitute this in the equation: 𝑥2𝑎+2𝑥(𝑚𝑥)ℎ+(𝑚𝑥)2𝑏=0 𝑥2(1𝑎+2𝑚ℎ+𝑚2𝑏)=0 So the slopes are given by 𝑚2𝑏+2𝑚ℎ+1𝑎=0 Let the two slopes be 𝑚 and 2𝑚. For the quadratic in slopes, 1𝑏𝑚2+2ℎ𝑚+1𝑎=0 Product of roots: 𝑚⋅2𝑚=1𝑎1𝑏 2𝑚2=𝑏𝑎 So, 𝑚2=𝑏2𝑎 Sum of roots: 𝑚+2𝑚=−2ℎ1𝑏 3𝑚=−2𝑏ℎ Squaring both sides, 9𝑚2=4𝑏2ℎ2 Now put 𝑚2=𝑏2𝑎: 9⋅𝑏2𝑎=4𝑏2ℎ2 ℎ2=8𝑎𝑏9 Hence, ℎ2:𝑎𝑏=8:9 So the correct option is 8:9 Option C.
Q 9MathematicsSection A • MCQcircle+2 / -0If the equation 3𝑥2+(3−𝑝)𝑥𝑦+𝑞𝑦2−2𝑝𝑥=8𝑝𝑞 represents a circle, then the area (in sq. units) of this circle is5𝜋Incorrect9𝜋Incorrect25𝜋Incorrect81𝜋IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (C)Step-by-Step Solution:For a second degree equation to represent a circle, the coefficients of 𝑥2 and 𝑦2 must be equal, and the coefficient of 𝑥𝑦 must be zero. Given equation: 3𝑥2+(3−𝑝)𝑥𝑦+𝑞𝑦2−2𝑝𝑥=8𝑝𝑞 For it to be a circle, 3−𝑝=0 So, 𝑝=3 Also, the coefficient of 𝑦2 must be equal to the coefficient of 𝑥2: 𝑞=3 Now substitute 𝑝=3 and 𝑞=3 in the equation: 3𝑥2+3𝑦2−6𝑥=8(3)(3) 3𝑥2+3𝑦2−6𝑥=72 Divide by 3: 𝑥2+𝑦2−2𝑥=24 Complete the square: 𝑥2−2𝑥+𝑦2=24 (𝑥−1)2−1+𝑦2=24 (𝑥−1)2+𝑦2=25 This is a circle with radius 𝑟=5. Area of the circle: 𝜋𝑟2=𝜋(5)2=25𝜋 So, the correct option is 25𝜋 Option C.
Q 10MathematicsSection A • MCQellipse+2 / -0The ellipse 4𝑥2+9𝑦2=1 intersects positive Y-axis at point A. If S and S' are its foci, then the area (in sq. units) of Δ𝑆𝐴𝑆′ is _____√512Incorrect√518Incorrect2√5Incorrect3√5IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (B)Step-by-Step Solution:The ellipse is 4𝑥2+9𝑦2=1 Write it in standard form: 𝑥214+𝑦219=1 Here, 𝑎2=14,𝑏2=19 Since 14>19, the major axis is along the 𝑥-axis. So, 𝑎=12,𝑏=13 For an ellipse, the foci are at (±𝑐,0), where 𝑐2=𝑎2−𝑏2 So, 𝑐2=14−19=9−436=536 Hence, 𝑐=√56 So the foci are 𝑆(√56,0),𝑆′(−√56,0) The ellipse intersects the positive 𝑌-axis at 𝐴. On the 𝑌-axis, 𝑥=0. 9𝑦2=1 𝑦=13 So, 𝐴=(0,13) Now, in △𝑆𝐴𝑆′: Base: 𝑆𝑆′=2𝑐=2⋅√56=√53 Height from 𝐴 to 𝑆𝑆′ is: 13 Area of triangle: 12×√53×13=√518 So the area is √518 Correct option: B.
Q 11MathematicsSection A • MCQlimits continuity and differentiability+2 / -0lim𝑥→1[𝑥−2𝑥2−𝑥−1𝑥3−3𝑥2+2𝑥]=3Incorrect4Incorrect2Incorrect1IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (C)Step-by-Step Solution:Given limit is lim𝑥→1[𝑥−2𝑥2−𝑥−1𝑥3−3𝑥2+2𝑥] First factor the denominators: 𝑥2−𝑥=𝑥(𝑥−1) and 𝑥3−3𝑥2+2𝑥=𝑥(𝑥2−3𝑥+2)=𝑥(𝑥−1)(𝑥−2) So the expression becomes 𝑥−2𝑥(𝑥−1)−1𝑥(𝑥−1)(𝑥−2) Take the common denominator 𝑥(𝑥−1)(𝑥−2): (𝑥−2)2−1𝑥(𝑥−1)(𝑥−2) Now simplify the numerator: (𝑥−2)2−1=𝑥2−4𝑥+4−1=𝑥2−4𝑥+3 𝑥2−4𝑥+3=(𝑥−1)(𝑥−3) So, (𝑥−1)(𝑥−3)𝑥(𝑥−1)(𝑥−2) Cancel (𝑥−1): 𝑥−3𝑥(𝑥−2) Now put 𝑥=1: 1−31(1−2)=−2−1=2 So the value of the limit is 2 Correct option: Option C.
Q 12MathematicsSection A • MCQmathematical reasoning+2 / -0If 𝐴={1,2,3,4,5,6} then which of the following is not true?∃𝑥∈𝐴 such that 𝑥+3=9.Incorrect∃𝑥∈𝐴 such that 𝑥+2<9.Incorrect∀𝑥∈𝐴,𝑥+6≥10.Incorrect∃𝑥∈𝐴 such that 𝑥+6<10.IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (C)Step-by-Step Solution:For 𝐴={1,2,3,4,5,6}, we check each statement. Option A: ∃𝑥∈𝐴 such that 𝑥+3=9 This means there is at least one value of 𝑥 in 𝐴 for which 𝑥+3=9. If 𝑥=6, then 6+3=9 So Option A is true. Option B: ∃𝑥∈𝐴 such that 𝑥+2<9 If 𝑥=1, then 1+2=3<9 So Option B is true. Option C: ∀𝑥∈𝐴, 𝑥+6≥10 This means for every value of 𝑥 in 𝐴, 𝑥+6 should be greater than or equal to 10. But if 𝑥=1, then 1+6=7 and 7≱10 So Option C is false. Option D: ∃𝑥∈𝐴 such that 𝑥+6<10 If 𝑥=1, then 1+6=7<10 So Option D is true. Hence, the statement which is not true is: Option C
Q 13MathematicsSection A • MCQmathematical reasoning+2 / -0Consider the following statements𝑟: If 𝑝→𝑞 is false then 𝑝∨𝑞 is false.𝑠: If 𝑝↔𝑞 is false then 𝑝∨𝑞 is false.The truth values of 𝑟→𝑠 and 𝑠→𝑟 are respectively ____T, TIncorrectT, FIncorrectF, TIncorrectF, FIncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (A)Step-by-Step Solution:For 𝑝⇒𝑞 to be false, 𝑝 must be true and 𝑞 must be false. So in statement 𝑟: 𝑝=𝑇,𝑞=𝐹 Then 𝑝∨𝑞=𝑇∨𝐹=𝑇 But statement 𝑟 says 𝑝∨𝑞 is false. That is not true. So, 𝑟=𝐹 Now for 𝑝↔𝑞 to be false, 𝑝 and 𝑞 must have different truth values. So either 𝑝=𝑇, 𝑞=𝐹 or 𝑝=𝐹, 𝑞=𝑇 In both cases, 𝑝∨𝑞=𝑇 So the statement “𝑝∨𝑞 is false” is again not true. Hence, 𝑠=𝐹 Now we find the truth values: 𝑟⇒𝑠=𝐹⇒𝐹=𝑇 and 𝑠⇒𝑟=𝐹⇒𝐹=𝑇 So the truth values are 𝑇, 𝑇 Correct option: A.
Q 14MathematicsSection A • MCQproperties of triangles+2 / -0In triangle ABC, with usual notations, if the angles are in Arithmetic Progression and 3𝑐2=2𝑏2, then the measure of angle A is5𝜋12Incorrect7𝜋12Incorrect5𝜋6Incorrect7𝜋6IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (A)Step-by-Step Solution:Since the angles 𝐴,𝐵,𝐶 are in Arithmetic Progression, the middle angle is the average of the other two: 𝐴+𝐶=2𝐵 Also, in a triangle, 𝐴+𝐵+𝐶=𝜋 Using 𝐴+𝐶=2𝐵, we get 2𝐵+𝐵=𝜋 3𝐵=𝜋 𝐵=𝜋3 Now given, 3𝑐2=2𝑏2 So, 𝑐2𝑏2=23 Using the sine rule, 𝑐𝑏=sin𝐶sin𝐵 Squaring both sides, 𝑐2𝑏2=sin2𝐶sin2𝐵 Hence, sin2𝐶sin2𝐵=23 Since 𝐵=𝜋3, sin𝐵=sin𝜋3=√32 So, sin2𝐵=34 Thus, sin2𝐶=23×34 sin2𝐶=12 So, sin𝐶=1√2 This gives 𝐶=𝜋4 Now, 𝐴+𝐵+𝐶=𝜋 𝐴+𝜋3+𝜋4=𝜋 𝐴=𝜋−𝜋3−𝜋4 𝐴=12𝜋−4𝜋−3𝜋12 𝐴=5𝜋12 So the measure of angle 𝐴 is 5𝜋12 Correct option: A.
Q 15MathematicsSection A • MCQmatrices and determinants+2 / -0If 𝐴=⎡⎣⎢00−10−10−100⎤⎦⎥ then which of the following is true ?𝐴2=𝐴−1Incorrect𝐴=−(adj𝐴)Incorrect𝐴−1=𝐴Incorrect𝐴−1=−𝐴IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (C)Step-by-Step Solution:Given 𝐴=⎡⎣⎢00−10−10−100⎤⎦⎥ First find 𝐴2. 𝐴2=𝐴⋅𝐴 𝐴2=⎡⎣⎢00−10−10−100⎤⎦⎥⎡⎣⎢00−10−10−100⎤⎦⎥ Multiplying row by column, 𝐴2=⎡⎣⎢100010001⎤⎦⎥=𝐼 So, 𝐴2=𝐼 This means 𝐴⋅𝐴=𝐼 By the definition of inverse matrix, if 𝐴⋅𝐵=𝐼 then 𝐵=𝐴−1. Here, 𝐵=𝐴 itself. Hence, 𝐴−1=𝐴 So the true option is Option C: 𝐴−1=𝐴
Q 16MathematicsSection A • MCQmatrices and determinants+2 / -0If ⎡⎣⎢21−1−1211−12⎤⎦⎥⎡⎣⎢𝑎𝑏𝑐⎤⎦⎥=⎡⎣⎢40−2⎤⎦⎥ then the distance of point 𝑃(𝑎,𝑏,𝑐) from the plane 2𝑥+𝑦+2𝑧=10 is2 units.Incorrect3 units.Incorrect4 units.Incorrect5 units.IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (B)Step-by-Step Solution:The given matrix equation means ⎡⎣⎢21−1−1211−12⎤⎦⎥⎡⎣⎢𝑎𝑏𝑐⎤⎦⎥=⎡⎣⎢40−2⎤⎦⎥ So we get the system of linear equations: 2𝑎+𝑏−𝑐=4 −𝑎+2𝑏+𝑐=0 𝑎−𝑏+2𝑐=−2 Solving these equations gives 𝑎=1,𝑏=1,𝑐=−1 So the point is 𝑃(1,1,−1) Now, the distance of a point (𝑥1,𝑦1,𝑧1) from the plane 𝐴𝑥+𝐵𝑦+𝐶𝑧+𝐷=0 is |𝐴𝑥1+𝐵𝑦1+𝐶𝑧1+𝐷|√𝐴2+𝐵2+𝐶2 The given plane is 2𝑥+𝑦+2𝑧=10 or 2𝑥+𝑦+2𝑧−10=0 Here, 𝐴=2,𝐵=1,𝐶=2,𝐷=−10 Using 𝑃(1,1,−1), Distance=|2(1)+1(1)+2(−1)−10|√22+12+22 =|2+1−2−10|√4+1+4 =|−9|3 =3 So, the distance is 3 units Correct option: Option B.
Q 17MathematicsSection A • MCQinverse trigonometric functions+2 / -0If cot(cos−1𝑥)=sec(tan−1𝑎√𝑏2−𝑎2), then the value of 𝑥 is𝑏√2𝑏2+𝑎2Incorrect√2𝑏2−𝑎2𝑏Incorrect√2𝑏2+𝑎2𝑏Incorrect𝑏√2𝑏2−𝑎2IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (D)Step-by-Step Solution:Take 𝜃=cos−1𝑥 So, cos𝜃=𝑥 Using a right triangle, if cos𝜃=𝑥, then sin𝜃=√1−𝑥2 So, cot(cos−1𝑥)=cot𝜃=cos𝜃sin𝜃=𝑥√1−𝑥2 Now take 𝜙=tan−1(𝑎√𝑏2−𝑎2) So, tan𝜙=𝑎√𝑏2−𝑎2 In a right triangle, perpendicular =𝑎 base =√𝑏2−𝑎2 Then hypotenuse is √𝑎2+(𝑏2−𝑎2)=√𝑏2=𝑏 So, sec𝜙=hypotenusebase=𝑏√𝑏2−𝑎2 Given, cot(cos−1𝑥)=sec(tan−1𝑎√𝑏2−𝑎2) So, 𝑥√1−𝑥2=𝑏√𝑏2−𝑎2 Squaring both sides, 𝑥21−𝑥2=𝑏2𝑏2−𝑎2 Cross-multiply: 𝑥2(𝑏2−𝑎2)=𝑏2(1−𝑥2) 𝑥2𝑏2−𝑥2𝑎2=𝑏2−𝑏2𝑥2 𝑥2(2𝑏2−𝑎2)=𝑏2 𝑥2=𝑏22𝑏2−𝑎2 So, 𝑥=𝑏√2𝑏2−𝑎2 Hence, the correct option is Option D 𝑏√2𝑏2−𝑎2
Q 18MathematicsSection A • MCQfunctions+2 / -0If 𝑔(𝑥)=𝑥2+𝑥−2 and 12(𝑔∘𝑓)(𝑥)=2𝑥2−5𝑥+2 then 𝑓(𝑥) is equal to2𝑥+3Incorrect2𝑥−3Incorrect2𝑥2+3𝑥+2Incorrect2𝑥2−3𝑥−2IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (B)Step-by-Step Solution:Given 𝑔(𝑥)=𝑥2+𝑥−2 and 12(𝑔∘𝑓)(𝑥)=2𝑥2−5𝑥+2 So, (𝑔∘𝑓)(𝑥)=2(2𝑥2−5𝑥+2) 𝑔(𝑓(𝑥))=4𝑥2−10𝑥+4 Now, since 𝑔(𝑥)=𝑥2+𝑥−2 we have 𝑔(𝑓(𝑥))=(𝑓(𝑥))2+𝑓(𝑥)−2 So we need a function 𝑓(𝑥) such that (𝑓(𝑥))2+𝑓(𝑥)−2=4𝑥2−10𝑥+4 Now check option B: 𝑓(𝑥)=2𝑥−3 Then 𝑔(𝑓(𝑥))=𝑔(2𝑥−3) =(2𝑥−3)2+(2𝑥−3)−2 =4𝑥2−12𝑥+9+2𝑥−3−2 =4𝑥2−10𝑥+4 This matches the required value. Hence, 𝑓(𝑥)=2𝑥−3 Correct option: B.
Q 19MathematicsSection A • MCQlimits continuity and differentiability+2 / -0Let the function f be defined by 𝑓(𝑥)=𝑥−|𝑥|𝑥, for 𝑥≠0 and 𝑓(0)=2 then f iscontinuous nowhereIncorrectcontinuous for all 𝑥 except at 𝑥=0Incorrectcontinuous everywhereIncorrectcontinuous for all 𝑥 except at 𝑥=1IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (B)Step-by-Step Solution:For 𝑥≠0, 𝑓(𝑥)=𝑥−|𝑥|𝑥 We check the value of |𝑥| in two cases. For 𝑥>0, we have |𝑥|=𝑥. So, 𝑓(𝑥)=𝑥−𝑥𝑥=0 For 𝑥<0, we have |𝑥|=−𝑥. So, 𝑓(𝑥)=𝑥−(−𝑥)𝑥=2𝑥𝑥=2 Also, it is given that 𝑓(0)=2 So the function can be written as 𝑓(𝑥)=⎧⎩⎨2,𝑥<02,𝑥=00,𝑥>0 For all 𝑥<0, the function is constant, so it is continuous. For all 𝑥>0, the function is also constant, so it is continuous. Now check at 𝑥=0: lim𝑥→0−𝑓(𝑥)=2 and lim𝑥→0+𝑓(𝑥)=0 Since the left-hand limit and right-hand limit are not equal, the limit at 𝑥=0 does not exist. So 𝑓 is not continuous at 𝑥=0. Hence, 𝑓 is continuous for all 𝑥 except at 𝑥=0. The correct option is: Option B
Q 20MathematicsSection A • MCQdifferentiation+2 / -0The derivative of tan−1(√1+𝑥2−1𝑥) with respect to sin−1(2𝑥1+𝑥2) is...12Incorrect14Incorrect1Incorrect2IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (B)Step-by-Step Solution:Take 𝑦=tan−1(√1+𝑥2−1𝑥) and 𝑧=sin−1(2𝑥1+𝑥2) We need 𝑑𝑦𝑑𝑧=𝑑𝑦𝑑𝑥𝑑𝑧𝑑𝑥 First simplify 𝑦. Rationalise the expression inside tan−1: √1+𝑥2−1𝑥=𝑥√1+𝑥2+1 Now we use the standard identity tan−1(𝑥√1+𝑥2+1)=12tan−1𝑥 So, 𝑦=12tan−1𝑥 Differentiating, 𝑑𝑦𝑑𝑥=12⋅11+𝑥2=12(1+𝑥2) Now consider 𝑧=sin−1(2𝑥1+𝑥2) Using the identity sin−1(2𝑥1+𝑥2)=2tan−1𝑥 for the usual principal range, we get 𝑧=2tan−1𝑥 Differentiating, 𝑑𝑧𝑑𝑥=2⋅11+𝑥2=21+𝑥2 Hence, 𝑑𝑦𝑑𝑧=12(1+𝑥2)21+𝑥2 𝑑𝑦𝑑𝑧=14 So the correct option is 14 Option B.
Q 21MathematicsSection A • MCQdifferentiation+2 / -0If the derivative of tan−1(𝑎+𝑏𝑥) with respect to x at 𝑥=0 is 1, then 𝑎6−𝑏3=3𝑎2𝑏−1Incorrect−3𝑎𝑏2+1Incorrect−1−3𝑎2𝑏Incorrect1+3𝑎𝑏2IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (C)Step-by-Step Solution:The given function is tan−1(𝑎+𝑏𝑥) Its derivative with respect to 𝑥 is 𝑑𝑑𝑥(tan−1(𝑎+𝑏𝑥))=𝑏1+(𝑎+𝑏𝑥)2 At 𝑥=0, the derivative is given as 1. So, 𝑏1+𝑎2=1 This gives 𝑏=1+𝑎2 Now we need to find 𝑎6−𝑏3 Since 𝑏=1+𝑎2 we get 𝑏3=(1+𝑎2)3 Using expansion, (1+𝑎2)3=1+3𝑎2+3𝑎4+𝑎6 So, 𝑎6−𝑏3=𝑎6−(1+3𝑎2+3𝑎4+𝑎6) =−1−3𝑎2−3𝑎4 Now, 3𝑎2𝑏=3𝑎2(1+𝑎2)=3𝑎2+3𝑎4 Hence, 𝑎6−𝑏3=−1−3𝑎2𝑏 So the correct option is −1−3𝑎2𝑏 Option C.
Q 22MathematicsSection A • MCQdifferentiation+2 / -0If 𝑥3+𝑦3=6 and 𝑑2𝑦𝑑𝑥2⋅𝑑2𝑥𝑑𝑦2=𝑚(𝑥𝑦)𝑛, where 𝑚,𝑛∈𝑅 then 𝑚𝑛=36Incorrect9Incorrect6Incorrect4IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (A)Step-by-Step Solution:Given 𝑥3+𝑦3=6 Differentiate both sides with respect to 𝑥: 3𝑥2+3𝑦2𝑑𝑦𝑑𝑥=0 So, 𝑑𝑦𝑑𝑥=−𝑥2𝑦2 Now differentiate again with respect to 𝑥: 𝑑2𝑦𝑑𝑥2=𝑑𝑑𝑥(−𝑥2𝑦2) Writing it as −𝑥2𝑦−2, 𝑑2𝑦𝑑𝑥2=−2𝑥𝑦−2+2𝑥2𝑦−3𝑑𝑦𝑑𝑥 Substitute 𝑑𝑦𝑑𝑥=−𝑥2𝑦2: 𝑑2𝑦𝑑𝑥2=−2𝑥𝑦2−2𝑥4𝑦5 Take common factor: 𝑑2𝑦𝑑𝑥2=−2𝑥(𝑦3+𝑥3)𝑦5 Since 𝑥3+𝑦3=6, 𝑑2𝑦𝑑𝑥2=−12𝑥𝑦5 Similarly, differentiating 𝑥3+𝑦3=6 with respect to 𝑦: 3𝑥2𝑑𝑥𝑑𝑦+3𝑦2=0 So, 𝑑𝑥𝑑𝑦=−𝑦2𝑥2 Differentiating again with respect to 𝑦 gives 𝑑2𝑥𝑑𝑦2=−12𝑦𝑥5 Now multiply both second derivatives: 𝑑2𝑦𝑑𝑥2⋅𝑑2𝑥𝑑𝑦2=(−12𝑥𝑦5)(−12𝑦𝑥5) =144𝑥𝑦𝑥5𝑦5 =144𝑥4𝑦4 =144(𝑥𝑦)4 Comparing with 𝑚(𝑥𝑦)𝑛 we get 𝑚=144,𝑛=4 Hence, 𝑚𝑛=1444=36 So the correct option is 36 Option A.
Q 23MathematicsSection A • MCQdifferentiation+2 / -0If 𝑥=sin(𝑡),𝑦=cos(𝑝𝑡), then (1−𝑥2)𝑑2𝑦𝑑𝑥2−𝑥𝑑𝑦𝑑𝑥=0Incorrect−𝑝2𝑦Incorrect𝑝2𝑦Incorrect𝑝IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (B)Step-by-Step Solution:Given 𝑥=sin𝑡,𝑦=cos(𝑝𝑡) First find 𝑑𝑦𝑑𝑥 using parametric differentiation: 𝑑𝑦𝑑𝑥=𝑑𝑦𝑑𝑡𝑑𝑥𝑑𝑡 Now, 𝑑𝑥𝑑𝑡=cos𝑡 and 𝑑𝑦𝑑𝑡=−𝑝sin(𝑝𝑡) So, 𝑑𝑦𝑑𝑥=−𝑝sin(𝑝𝑡)cos𝑡 Now differentiate again with respect to 𝑥: 𝑑2𝑦𝑑𝑥2=1𝑑𝑥𝑑𝑡𝑑𝑑𝑡(𝑑𝑦𝑑𝑥) 𝑑2𝑦𝑑𝑥2=1cos𝑡𝑑𝑑𝑡(−𝑝sin(𝑝𝑡)sec𝑡) Using product rule, 𝑑2𝑦𝑑𝑥2=1cos𝑡[−𝑝2cos(𝑝𝑡)sec𝑡−𝑝sin(𝑝𝑡)sec𝑡tan𝑡] 𝑑2𝑦𝑑𝑥2=−𝑝2cos(𝑝𝑡)sec2𝑡−𝑝sin(𝑝𝑡)sec2𝑡tan𝑡 Now, 1−𝑥2=1−sin2𝑡=cos2𝑡 and 𝑥=sin𝑡 So, (1−𝑥2)𝑑2𝑦𝑑𝑥2−𝑥𝑑𝑦𝑑𝑥 =cos2𝑡[−𝑝2cos(𝑝𝑡)sec2𝑡−𝑝sin(𝑝𝑡)sec2𝑡tan𝑡]−sin𝑡(−𝑝sin(𝑝𝑡)cos𝑡) =−𝑝2cos(𝑝𝑡)−𝑝sin(𝑝𝑡)tan𝑡+𝑝sin(𝑝𝑡)tan𝑡 The last two terms cancel: =−𝑝2cos(𝑝𝑡) Since 𝑦=cos(𝑝𝑡), (1−𝑥2)𝑑2𝑦𝑑𝑥2−𝑥𝑑𝑦𝑑𝑥=−𝑝2𝑦 So the correct option is −𝑝2𝑦 Option B.
Q 24MathematicsSection A • MCQapplication of derivatives+2 / -0If the function 𝑓(𝑥)=𝑎𝑥3+𝑏𝑥2+11𝑥−6, defined on [1,3], satisfies all the conditions of Rolle's theorem for 𝑐=2+1√3, then𝑎=−1,𝑏=12Incorrect𝑎=1,𝑏=−6Incorrect𝑎=−1,𝑏=6Incorrect𝑎=−2,𝑏=1IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (B)Step-by-Step Solution:Since 𝑓(𝑥)=𝑎𝑥3+𝑏𝑥2+11𝑥−6 is a polynomial, it is continuous on [1,3] and differentiable on (1,3) automatically. For Rolle’s theorem, we need 𝑓(1)=𝑓(3) and the given value 𝑐=2+1√3 must satisfy 𝑓′(𝑐)=0 First, use 𝑓(1)=𝑓(3). 𝑓(1)=𝑎+𝑏+11−6=𝑎+𝑏+5 𝑓(3)=27𝑎+9𝑏+33−6=27𝑎+9𝑏+27 So, 𝑎+𝑏+5=27𝑎+9𝑏+27 26𝑎+8𝑏+22=0 Dividing by 2, 13𝑎+4𝑏+11=0 Now, 𝑓′(𝑥)=3𝑎𝑥2+2𝑏𝑥+11 Since 𝑓′(𝑐)=0, 3𝑎(2+1√3)2+2𝑏(2+1√3)+11=0 Now, (2+1√3)2=4+4√3+13=133+4√3 So, 3𝑎(133+4√3)+2𝑏(2+1√3)+11=0 13𝑎+12𝑎√3+4𝑏+2𝑏√3+11=0 Using 12√3=4√3 and 2√3=2√33, 13𝑎+4𝑏+11+4√3𝑎+2√33𝑏=0 But from earlier, 13𝑎+4𝑏+11=0 So the remaining part must be zero: 4√3𝑎+2√33𝑏=0 Divide by √3: 4𝑎+2𝑏3=0 Multiplying by 3, 12𝑎+2𝑏=0 𝑏=−6𝑎 Substitute this in 13𝑎+4𝑏+11=0 13𝑎+4(−6𝑎)+11=0 13𝑎−24𝑎+11=0 −11𝑎+11=0 𝑎=1 Then 𝑏=−6(1)=−6 So, 𝑎=1,𝑏=−6 Hence, the correct option is: Option B
Q 25MathematicsSection A • MCQapplication of derivatives+2 / -0The tangent to the curve 𝑦2−𝑥𝑦+9=0 is vertical when𝑦=0Incorrect𝑦=±√3Incorrect𝑦=12Incorrect𝑦=±3IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (D)Step-by-Step Solution:For the curve 𝑦2−𝑥𝑦+9=0 we differentiate implicitly with respect to 𝑥. 𝑑𝑑𝑥(𝑦2)−𝑑𝑑𝑥(𝑥𝑦)+𝑑𝑑𝑥(9)=0 Using product rule for 𝑥𝑦, 2𝑦𝑑𝑦𝑑𝑥−(𝑥𝑑𝑦𝑑𝑥+𝑦)=0 So, 2𝑦𝑑𝑦𝑑𝑥−𝑥𝑑𝑦𝑑𝑥−𝑦=0 (2𝑦−𝑥)𝑑𝑦𝑑𝑥=𝑦 Hence, 𝑑𝑦𝑑𝑥=𝑦2𝑦−𝑥 A tangent is vertical when its slope is undefined, that is, when the denominator becomes zero. So, 2𝑦−𝑥=0 𝑥=2𝑦 Now put 𝑥=2𝑦 in the original curve: 𝑦2−(2𝑦)𝑦+9=0 𝑦2−2𝑦2+9=0 −𝑦2+9=0 𝑦2=9 𝑦=±3 So, the tangent is vertical when 𝑦=±3 Correct option: Option D.
Q 26MathematicsSection A • MCQapplication of derivatives+2 / -0The value of 𝑘 such that the function 𝑓(𝑥)=sin𝑥−cos𝑥−𝑘𝑥+𝑏 is strictly decreasing for all real 𝑥 is𝑘<1Incorrect𝑘>1Incorrect𝑘<√2Incorrect𝑘>√2IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (D)Step-by-Step Solution:For the function 𝑓(𝑥)=sin𝑥−cos𝑥−𝑘𝑥+𝑏 differentiate with respect to 𝑥: 𝑓′(𝑥)=cos𝑥+sin𝑥−𝑘 For 𝑓(𝑥) to be strictly decreasing for all real 𝑥, we need 𝑓′(𝑥)<0 for all real 𝑥. Now, sin𝑥+cos𝑥 has maximum value √2 So the greatest possible value of 𝑓′(𝑥) is √2−𝑘 For 𝑓′(𝑥) to remain negative for all 𝑥, √2−𝑘<0 So, 𝑘>√2 Hence the correct option is Option D 𝑘>√2
Q 27MathematicsSection A • MCQindefinite integration+2 / -0∫sin𝑥sin4𝑥𝑑𝑥=14√2log∣1+√2sin𝑥1−√2sin𝑥∣+14log|sec𝑥+tan𝑥|+𝑐Incorrect14√2log∣1+√2sin𝑥1−√2sin𝑥∣−14log|sec𝑥+tan𝑥|+𝑐Incorrect14√2log∣1−√2sin𝑥1+√2sin𝑥∣+14log|sec𝑥+tan𝑥|+𝑐Incorrect14√2log∣1−√2sin𝑥1+√2sin𝑥∣−14log|sec𝑥+tan𝑥|+𝑐IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (B)Step-by-Step Solution:∫sin𝑥sin4𝑥𝑑𝑥 Use the identity sin4𝑥=4sin𝑥cos𝑥cos2𝑥 So, sin𝑥sin4𝑥=sin𝑥4sin𝑥cos𝑥cos2𝑥=14cos𝑥cos2𝑥 Hence, ∫sin𝑥sin4𝑥𝑑𝑥=14∫𝑑𝑥cos𝑥cos2𝑥 Now use cos2𝑥=1−2sin2𝑥 So, 14∫𝑑𝑥cos𝑥(1−2sin2𝑥) Put 𝑡=sin𝑥 Then 𝑑𝑡=cos𝑥𝑑𝑥 So, 𝑑𝑥cos𝑥=𝑑𝑡cos2𝑥=𝑑𝑡1−sin2𝑥=𝑑𝑡1−𝑡2 Thus the integral becomes 14∫𝑑𝑡(1−𝑡2)(1−2𝑡2) Now, 1(1−𝑡2)(1−2𝑡2)=−11−𝑡2+21−2𝑡2 So, 𝐼=14[−∫𝑑𝑡1−𝑡2+2∫𝑑𝑡1−2𝑡2] We know, ∫𝑑𝑡1−𝑡2=12log∣1+𝑡1−𝑡∣ and ∫𝑑𝑡1−2𝑡2=12√2log∣1+√2𝑡1−√2𝑡∣ So, 𝐼=−14⋅12log∣1+𝑡1−𝑡∣+14⋅1√2log∣1+√2𝑡1−√2𝑡∣+𝑐 Since 𝑡=sin𝑥, 𝐼=14√2log∣1+√2sin𝑥1−√2sin𝑥∣−14log|sec𝑥+tan𝑥|+𝑐 So, the correct option is Option B
Q 28MathematicsSection A • MCQindefinite integration+2 / -0∫√4𝑥(4𝑥+4)𝑑𝑥=⋯1log2[2𝑥2√4𝑥+4+2log|2𝑥+√4𝑥+4|]+𝑐Incorrect2𝑥2√4𝑥+4+2log|2𝑥+√4𝑥+4|+𝑐Incorrect1log2[2𝑥2√4𝑥+4+log|2𝑥+√4𝑥+4|]+𝑐Incorrect[2𝑥log4√4𝑥+4+log|2𝑥+√4𝑥+4|]+𝑐IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (A)Step-by-Step Solution:Given, ∫√4𝑥(4𝑥+4)𝑑𝑥 First simplify the expression inside the square root. Since 4𝑥=(2𝑥)2 we get √4𝑥(4𝑥+4)=√(2𝑥)2(4𝑥+4)=2𝑥√4𝑥+4 So the integral becomes ∫2𝑥√4𝑥+4𝑑𝑥 Now put 𝑡=2𝑥 Then 𝑑𝑡𝑑𝑥=2𝑥log2 so 𝑑𝑡=2𝑥log2𝑑𝑥 Hence, 2𝑥𝑑𝑥=𝑑𝑡log2 Also, 4𝑥=(2𝑥)2=𝑡2 Therefore, ∫2𝑥√4𝑥+4𝑑𝑥=1log2∫√𝑡2+4𝑑𝑡 Using the standard formula, ∫√𝑡2+𝑎2𝑑𝑡=𝑡2√𝑡2+𝑎2+𝑎22log|𝑡+√𝑡2+𝑎2|+𝐶 Here 𝑎2=4, so ∫√𝑡2+4𝑑𝑡=𝑡2√𝑡2+4+2log|𝑡+√𝑡2+4|+𝐶 Substituting 𝑡=2𝑥, ∫√4𝑥(4𝑥+4)𝑑𝑥=1log2[2𝑥2√4𝑥+4+2log|2𝑥+√4𝑥+4|]+𝐶 So the correct option is Option A
Q 29MathematicsSection A • MCQindefinite integration+2 / -0The value of ∫1𝑥2−5𝑥+8𝑑𝑥 is equal to...2√7tan−1(2𝑥+5√7)+𝑐Incorrect−2√7tan−1(2𝑥−5√7)+𝑐Incorrect2√7tan−1(2𝑥−5√7)+𝑐Incorrect−2√7tan−1(2𝑥+5√7)+𝑐IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (C)Step-by-Step Solution:Given, ∫1𝑥2−5𝑥+8𝑑𝑥 First complete the square in the denominator: 𝑥2−5𝑥+8=(𝑥−52)2+8−254 =(𝑥−52)2+74 So the integral becomes ∫1(𝑥−52)2+74𝑑𝑥 Now write 74 as (√72)2: ∫1(𝑥−52)2+(√72)2𝑑𝑥 Using the standard formula, ∫𝑑𝑥𝑥2+𝑎2=1𝑎tan−1(𝑥𝑎)+𝐶 Here, 𝑎=√72 So, ∫1𝑥2−5𝑥+8𝑑𝑥=2√7tan−1(𝑥−52√72)+𝐶 Simplifying the argument, 𝑥−52√72=2𝑥−5√7 Hence, ∫1𝑥2−5𝑥+8𝑑𝑥=2√7tan−1(2𝑥−5√7)+𝐶 So the correct option is Option C
Q 30MathematicsSection A • MCQindefinite integration+2 / -0∫2𝑥4−3𝑥−𝑥2𝑑𝑥=⋯85log|4+𝑥|−25log|1−𝑥|+𝑐Incorrect2log|4+𝑥|+25log|1−𝑥|+𝑐Incorrect−log|4+𝑥|+25log|1−𝑥|+𝑐Incorrect−85log|4+𝑥|−25log|1−𝑥|+𝑐IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (D)Step-by-Step Solution:∫2𝑥4−3𝑥−𝑥2𝑑𝑥 First factor the denominator: 4−3𝑥−𝑥2=(𝑥+4)(1−𝑥) So, 2𝑥4−3𝑥−𝑥2=2𝑥(𝑥+4)(1−𝑥) Use partial fractions: 2𝑥(𝑥+4)(1−𝑥)=𝐴𝑥+4+𝐵1−𝑥 Multiplying by (𝑥+4)(1−𝑥), 2𝑥=𝐴(1−𝑥)+𝐵(𝑥+4) Expanding, 2𝑥=𝐴−𝐴𝑥+𝐵𝑥+4𝐵 2𝑥=(𝐴+4𝐵)+(−𝐴+𝐵)𝑥 Comparing coefficients, 𝐴+4𝐵=0 and −𝐴+𝐵=2 Solving these, 𝐴=−85,𝐵=25 So, 2𝑥4−3𝑥−𝑥2=−85⋅1𝑥+4+25⋅11−𝑥 Now integrate: ∫2𝑥4−3𝑥−𝑥2𝑑𝑥=−85∫1𝑥+4𝑑𝑥+25∫11−𝑥𝑑𝑥 Since ∫11−𝑥𝑑𝑥=−log|1−𝑥| we get −85log|𝑥+4|−25log|1−𝑥|+𝑐 So the correct option is Option D
Q 31MathematicsSection A • MCQdefinite integration+2 / -0If ∫𝑒2[1log𝑥−1(log𝑥)2]𝑑𝑥=𝑎+𝑏log2, then values of 𝑎 and 𝑏 are𝑎=𝑒,𝑏=2Incorrect𝑎=−𝑒,𝑏=2Incorrect𝑎=𝑒,𝑏=−2Incorrect𝑎=−𝑒,𝑏=−2IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (C)Step-by-Step Solution:The integrand is 1log𝑥−1(log𝑥)2 We notice that this looks like the derivative of 𝑥log𝑥. Using the quotient rule, 𝑑𝑑𝑥(𝑥log𝑥)=(log𝑥)(1)−𝑥(1𝑥)(log𝑥)2 =log𝑥−1(log𝑥)2 Now split it: log𝑥(log𝑥)2−1(log𝑥)2=1log𝑥−1(log𝑥)2 So, ∫2𝑒[1log𝑥−1(log𝑥)2]𝑑𝑥=[𝑥log𝑥]𝑒2 Now substitute the limits: =𝑒log𝑒−2log2 Since log𝑒=1, =𝑒−2log2 This is of the form 𝑎+𝑏log2 So, 𝑎=𝑒,𝑏=−2 Hence, the correct option is Option C
Q 32MathematicsSection A • MCQdefinite integration+2 / -0If ∫𝑘011+4𝑥𝑑𝑥=log2(43), then 𝑘= _____2√3Incorrect32Incorrect√32Incorrect23IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (B)Step-by-Step Solution:Given, ∫0𝑘11+4𝑥𝑑𝑥=log2(43) First, find the integral. We use the fact that 11+4𝑥=1−4𝑥1+4𝑥 So, ∫11+4𝑥𝑑𝑥=∫(1−4𝑥1+4𝑥)𝑑𝑥 Now, ∫4𝑥1+4𝑥𝑑𝑥=1ln4ln(1+4𝑥) Hence, ∫11+4𝑥𝑑𝑥=𝑥−log4(1+4𝑥) Now apply the limits from 0 to 𝑘: ∫0𝑘11+4𝑥𝑑𝑥=[𝑥−log4(1+4𝑥)]𝑘0 =𝑘−log4(1+4𝑘)+log42 Since log42=12, ∫0𝑘11+4𝑥𝑑𝑥=𝑘−log4(1+4𝑘)+12 Write 𝑘=log4(4𝑘) and 12=log42: =log4(4𝑘)−log4(1+4𝑘)+log42 =log4(2⋅4𝑘1+4𝑘) Given that this equals log2(43) Convert it to base 4: log2(43)=log4(43)2=log4(169) So, log4(2⋅4𝑘1+4𝑘)=log4(169) Thus, 2⋅4𝑘1+4𝑘=169 Let 4𝑘=𝑦. 2𝑦1+𝑦=169 18𝑦=16+16𝑦 2𝑦=16 𝑦=8 So, 4𝑘=8 Now write both sides as powers of 2: (22)𝑘=23 22𝑘=23 2𝑘=3 𝑘=32 So the correct option is 32 Option B.
Q 33MathematicsSection A • MCQarea under the curves+2 / -0The area bounded by the curve 𝑦=𝑥∣sin(𝑥2)∣ and the X-axis between the lines 𝑥=0 and 𝑥=4𝜋 (in square units), is....4𝜋Incorrect8𝜋Incorrect12𝜋Incorrect16𝜋IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (D)Step-by-Step Solution:The required area is ∫04𝜋𝑥∣sin(𝑥2)∣𝑑𝑥 Now, sin(𝑥2) changes sign in the interval 0 to 4𝜋. For 0≤𝑥≤2𝜋, sin(𝑥2)≥0 so, ∣sin(𝑥2)∣=sin(𝑥2) For 2𝜋≤𝑥≤4𝜋, sin(𝑥2)≤0 so, ∣sin(𝑥2)∣=−sin(𝑥2) Hence the area is 𝐴=∫02𝜋𝑥sin(𝑥2)𝑑𝑥−∫2𝜋4𝜋𝑥sin(𝑥2)𝑑𝑥 Put 𝑡=𝑥2 Then 𝑥=2𝑡,𝑑𝑥=2𝑑𝑡 The limits change as: 𝑥=0⇒𝑡=0 𝑥=4𝜋⇒𝑡=2𝜋 So, 𝐴=4∫02𝜋𝑡|sin𝑡|𝑑𝑡 Now split at 𝑡=𝜋: 𝐴=4[∫0𝜋𝑡sin𝑡𝑑𝑡+∫𝜋2𝜋−𝑡sin𝑡𝑑𝑡] Using integration by parts, ∫𝑡sin𝑡𝑑𝑡=−𝑡cos𝑡+sin𝑡 So, ∫0𝜋𝑡sin𝑡𝑑𝑡=[−𝑡cos𝑡+sin𝑡]𝜋0=𝜋 Also, ∫𝜋2𝜋−𝑡sin𝑡𝑑𝑡=[𝑡cos𝑡−sin𝑡]2𝜋𝜋=3𝜋 Thus, 𝐴=4[𝜋+3𝜋] 𝐴=16𝜋 So the correct option is 16𝜋 Option D.
Q 34MathematicsSection A • MCQarea under the curves+2 / -0If the area enclosed between the curves 𝑦2=4𝑘𝑥 and 𝑦=𝑘𝑥,𝑘>0 is 2𝑘3 sq. units then 𝑘=1Incorrect1.5Incorrect2Incorrect3IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (C)Step-by-Step Solution:The curves are 𝑦2=4𝑘𝑥 and 𝑦=𝑘𝑥,𝑘>0 First find their points of intersection. From 𝑦=𝑘𝑥, we get 𝑥=𝑦𝑘 Substitute this in 𝑦2=4𝑘𝑥: 𝑦2=4𝑘(𝑦𝑘) 𝑦2=4𝑦 𝑦(𝑦−4)=0 So, 𝑦=0or𝑦=4 The corresponding points are 𝑦=0⇒𝑥=0 and 𝑦=4⇒𝑥=4𝑘 Now write both curves in terms of 𝑥 as functions of 𝑦: For the parabola, 𝑥=𝑦24𝑘 For the line, 𝑥=𝑦𝑘 Between 𝑦=0 and 𝑦=4, the line is to the right of the parabola. So the enclosed area is ∫04(𝑦𝑘−𝑦24𝑘)𝑑𝑦 =1𝑘∫04(𝑦−𝑦24)𝑑𝑦 =1𝑘[𝑦22−𝑦312]40 =1𝑘(8−6412) =1𝑘(8−163) =1𝑘⋅83 =83𝑘 Given area is 2𝑘3 So, 83𝑘=2𝑘3 8=2𝑘2 𝑘2=4 Since 𝑘>0, 𝑘=2 Hence, the correct option is 2 Option C.
Q 35MathematicsSection A • MCQdifferential equations+2 / -0The solution of the differential equation 2𝑥𝑑𝑦𝑑𝑥−𝑦=3 represents a family ofstraight linesIncorrectcirclesIncorrectparabolaIncorrectellipseIncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (C)Step-by-Step Solution:Given differential equation is 2𝑥𝑑𝑦𝑑𝑥−𝑦=3 Rearrange it as 2𝑥𝑑𝑦𝑑𝑥=𝑦+3 So, 𝑑𝑦𝑑𝑥=𝑦+32𝑥 Separate the variables: 𝑑𝑦𝑦+3=𝑑𝑥2𝑥 Integrating both sides, ∫𝑑𝑦𝑦+3=∫𝑑𝑥2𝑥 log|𝑦+3|=12log|𝑥|+log𝐶 This gives 𝑦+3=𝐶√𝑥 Squaring both sides, (𝑦+3)2=𝐶2𝑥 This is of the form 𝑌2=4𝑎𝑋 which represents a parabola. So, the solution represents a family of parabolas. The correct option is: Option C: parabola
Q 36MathematicsSection A • MCQdifferential equations+2 / -0The solution of the differential equation 𝑥𝑑𝑦𝑑𝑥+𝑦=𝑥3𝑦6, is...𝑦5=52𝑥−3+𝑐𝑥5Incorrect𝑦5=52𝑥3+𝑐𝑥5Incorrect1𝑦5=52𝑥−3+𝑐𝑥5Incorrect1𝑦5=52𝑥3+𝑐𝑥5IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (D)Step-by-Step Solution:Given, 𝑥𝑑𝑦𝑑𝑥+𝑦=𝑥3𝑦6 Divide by 𝑥: 𝑑𝑦𝑑𝑥+1𝑥𝑦=𝑥2𝑦6 This is a Bernoulli differential equation of the form 𝑑𝑦𝑑𝑥+𝑃𝑦=𝑄𝑦𝑛 Here, 𝑛=6. For Bernoulli equation, put 𝑣=𝑦1−𝑛=𝑦−5=1𝑦5 Now, 𝑣=𝑦−5 Differentiating, 𝑑𝑣𝑑𝑥=−5𝑦−6𝑑𝑦𝑑𝑥 Multiply the differential equation 𝑑𝑦𝑑𝑥+1𝑥𝑦=𝑥2𝑦6 by 𝑦−6: 𝑦−6𝑑𝑦𝑑𝑥+1𝑥𝑦−5=𝑥2 Using 𝑣=𝑦−5 and 𝑦−6𝑑𝑦𝑑𝑥=−15𝑑𝑣𝑑𝑥, −15𝑑𝑣𝑑𝑥+1𝑥𝑣=𝑥2 Multiply by −5: 𝑑𝑣𝑑𝑥−5𝑥𝑣=−5𝑥2 This is a linear differential equation. Its integrating factor is 𝑒∫−5𝑥𝑑𝑥=𝑒−5ln𝑥=𝑥−5 So, 𝑑𝑑𝑥(𝑣𝑥−5)=−5𝑥2⋅𝑥−5 𝑑𝑑𝑥(𝑣𝑥−5)=−5𝑥−3 Integrating, 𝑣𝑥−5=∫−5𝑥−3𝑑𝑥 𝑣𝑥−5=52𝑥−2+𝑐 Multiply by 𝑥5: 𝑣=52𝑥3+𝑐𝑥5 Since 𝑣=1𝑦5, 1𝑦5=52𝑥3+𝑐𝑥5 So, the correct option is Option D
Q 37MathematicsSection A • MCQvector algebra+2 / -0If 𝑎¯=𝑖ˆ+𝑗ˆ+𝑘ˆ,𝑏¯=𝑖ˆ−𝑗ˆ+2𝑘ˆ and 𝑐¯=𝑥𝑖ˆ+(𝑥−2)𝑗ˆ−𝑘ˆ are three vectors in which 𝑐¯ lies in the plane of 𝑎¯ and 𝑏¯, then 𝑥=⋯0Incorrect1Incorrect−4Incorrect−2IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (D)Step-by-Step Solution:Since 𝑐¯ lies in the plane of 𝑎¯ and 𝑏¯, the three vectors 𝑎¯,𝑏¯,𝑐¯ are coplanar. For three vectors to be coplanar, their scalar triple product must be zero: [𝑎¯ 𝑏¯ 𝑐¯]=0 Given, 𝑎¯=𝑖ˆ+𝑗ˆ+𝑘ˆ 𝑏¯=𝑖ˆ−𝑗ˆ+2𝑘ˆ 𝑐¯=𝑥𝑖ˆ+(𝑥−2)𝑗ˆ−𝑘ˆ So, ∣1111−12𝑥𝑥−2−1∣=0 Expanding along the first row, 1∣−12𝑥−2−1∣−1∣12𝑥−1∣+1∣1−1𝑥𝑥−2∣=0 Now simplify: [(−1)(−1)−2(𝑥−2)]−[1(−1)−2𝑥]+[1(𝑥−2)−(−1)𝑥]=0 [1−2𝑥+4]−[−1−2𝑥]+[𝑥−2+𝑥]=0 (5−2𝑥)+(1+2𝑥)+(2𝑥−2)=0 2𝑥+4=0 2𝑥=−4 𝑥=−2 So, the correct option is: −2 Option D.
Q 38MathematicsSection A • MCQvector algebra+2 / -0If |𝑎¯|=4,|𝑏¯|=3 and 𝑎¯⋅𝑏¯=8 then [𝑎¯ 𝑎¯+𝑏¯ 𝑎¯×𝑏¯]=96Incorrect80Incorrect64Incorrect120IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (B)Step-by-Step Solution:We need to find [𝑎⃗ 𝑎⃗+𝑏⃗ 𝑎⃗×𝑏⃗] The scalar triple product is written as [𝑥⃗ 𝑦⃗ 𝑧⃗]=𝑥⃗⋅(𝑦⃗×𝑧⃗) Using the property of scalar triple product, [𝑎⃗ 𝑎⃗+𝑏⃗ 𝑎⃗×𝑏⃗] can be split as [𝑎⃗ 𝑎⃗ 𝑎⃗×𝑏⃗]+[𝑎⃗ 𝑏⃗ 𝑎⃗×𝑏⃗] Now, [𝑎⃗ 𝑎⃗ 𝑎⃗×𝑏⃗]=0 because two vectors are the same. So, [𝑎⃗ 𝑎⃗+𝑏⃗ 𝑎⃗×𝑏⃗]=[𝑎⃗ 𝑏⃗ 𝑎⃗×𝑏⃗] Now, [𝑎⃗ 𝑏⃗ 𝑎⃗×𝑏⃗]=(𝑎⃗×𝑏⃗)⋅(𝑎⃗×𝑏⃗) So, [𝑎⃗ 𝑏⃗ 𝑎⃗×𝑏⃗]=|𝑎⃗×𝑏⃗|2 We know, |𝑎⃗×𝑏⃗|2=|𝑎⃗|2|𝑏⃗|2−(𝑎⃗⋅𝑏⃗)2 Given: |𝑎⃗|=4,|𝑏⃗|=3,𝑎⃗⋅𝑏⃗=8 So, |𝑎⃗×𝑏⃗|2=42⋅32−82 =16⋅9−64 =144−64 =80 Hence, [𝑎⃗ 𝑎⃗+𝑏⃗ 𝑎⃗×𝑏⃗]=80 So the correct option is Option B: 80.
Q 39MathematicsSection A • MCQvector algebra+2 / -0Let 𝑎¯,𝑏¯,𝑐¯ be the unit vectors such that 𝑎¯ is perpendicular to 𝑏¯ and the angle between 𝑏¯ and 𝑐¯ is 120∘. If 𝑎¯+𝑐¯ is perpendicular to 𝑏¯+𝑐¯ then(𝑎¯+𝑐¯)⋅(𝑏¯−𝑐¯)=1Incorrect(𝑎¯−𝑐¯)⋅(𝑏¯−𝑐¯)=−2Incorrect(𝑎¯−𝑐¯)⋅(𝑏¯+𝑐¯)=1Incorrect(𝑎¯−𝑐¯)⋅(𝑏¯−𝑐¯)=2IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (D)Step-by-Step Solution:Since 𝑎¯,𝑏¯,𝑐¯ are unit vectors, 𝑎¯⋅𝑏¯=0 because 𝑎¯ is perpendicular to 𝑏¯. Also, the angle between 𝑏¯ and 𝑐¯ is 120∘, so 𝑏¯⋅𝑐¯=|𝑏¯||𝑐¯|cos120∘ Since both are unit vectors, 𝑏¯⋅𝑐¯=1⋅1⋅(−12)=−12 Now, 𝑎¯+𝑐¯ is perpendicular to 𝑏¯+𝑐¯, so their dot product is zero: (𝑎¯+𝑐¯)⋅(𝑏¯+𝑐¯)=0 Expanding, 𝑎¯⋅𝑏¯+𝑎¯⋅𝑐¯+𝑐¯⋅𝑏¯+𝑐¯⋅𝑐¯=0 Substitute known values: 0+𝑎¯⋅𝑐¯−12+1=0 So, 𝑎¯⋅𝑐¯+12=0 Hence, 𝑎¯⋅𝑐¯=−12 Now check the given expressions. For Option D: (𝑎¯−𝑐¯)⋅(𝑏¯−𝑐¯) Expanding, =𝑎¯⋅𝑏¯−𝑎¯⋅𝑐¯−𝑐¯⋅𝑏¯+𝑐¯⋅𝑐¯ Substitute the values: =0−(−12)−(−12)+1 =12+12+1 =2 So the correct option is: Option D
Q 40MathematicsSection A • MCQvector algebra+2 / -0Let 𝑥0 be the point of local maxima of 𝑓(𝑥)=𝑎¯⋅(𝑏¯×𝑐¯) where 𝑎¯=𝑥𝑖ˆ−2𝑗ˆ+3𝑘ˆ,𝑏¯=−2𝑖ˆ+𝑥𝑗ˆ−𝑘ˆ and 𝑐¯=7𝑖ˆ−2𝑗ˆ+𝑥𝑘ˆ then the value of 𝑎¯⋅𝑐¯ at 𝑥=𝑥0 is26Incorrect0Incorrect−15Incorrect−26IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (D)Step-by-Step Solution:Given 𝑎⃗=𝑥𝑖ˆ−2𝑗ˆ+3𝑘ˆ,𝑏⃗=−2𝑖ˆ+𝑥𝑗ˆ−𝑘ˆ,𝑐⃗=7𝑖ˆ−2𝑗ˆ+𝑥𝑘ˆ We have 𝑓(𝑥)=𝑎⃗⋅(𝑏⃗×𝑐⃗) This is the scalar triple product, so we can write it as a determinant: 𝑓(𝑥)=∣𝑥−23−2𝑥−17−2𝑥∣ Expanding along the first row, 𝑓(𝑥)=𝑥∣𝑥−1−2𝑥∣−(−2)∣−2−17𝑥∣+3∣−2𝑥7−2∣ 𝑓(𝑥)=𝑥(𝑥2−2)+2(−2𝑥+7)+3(4−7𝑥) 𝑓(𝑥)=𝑥3−2𝑥−4𝑥+14+12−21𝑥 𝑓(𝑥)=𝑥3−27𝑥+26 For local maxima, differentiate: 𝑓′(𝑥)=3𝑥2−27 Set 𝑓′(𝑥)=0: 3𝑥2−27=0 𝑥2=9 𝑥=±3 Now, 𝑓′′(𝑥)=6𝑥 At 𝑥=−3, 𝑓′′(−3)=−18<0 So 𝑥0=−3 is the point of local maxima. Now find 𝑎⃗⋅𝑐⃗ at 𝑥=𝑥0=−3. 𝑎⃗⋅𝑐⃗=(𝑥)(7)+(−2)(−2)+(3)(𝑥) 𝑎⃗⋅𝑐⃗=7𝑥+4+3𝑥 𝑎⃗⋅𝑐⃗=10𝑥+4 At 𝑥=−3, 𝑎⃗⋅𝑐⃗=10(−3)+4=−30+4=−26 So the correct option is −26 Option D.
Q 41MathematicsSection A • MCQvector algebra+2 / -0The parallelopiped is determined by vectors 𝑎¯=−2𝑖ˆ+5𝑗ˆ+3𝑘ˆ, 𝑏¯=𝑖ˆ+3𝑗ˆ−2𝑘ˆ, 𝑐¯=−3𝑖ˆ+𝑗ˆ+4𝑘ˆ. The altitude of parallelopiped on the parallelogram base determined by vectors 𝑏¯ and 𝑐¯ is2√35Incorrect25Incorrect12Incorrect5√32IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (A)Step-by-Step Solution:The altitude of a parallelepiped on the base formed by vectors 𝑏⃗ and 𝑐⃗ is Altitude=Volume of parallelepipedArea of base Here, the base is the parallelogram determined by 𝑏⃗ and 𝑐⃗. So, Volume=|𝑎⃗⋅(𝑏⃗×𝑐⃗)| and Area of base=|𝑏⃗×𝑐⃗| Given, 𝑎⃗=−2𝑖ˆ+5𝑗ˆ+3𝑘ˆ 𝑏⃗=𝑖ˆ+3𝑗ˆ−2𝑘ˆ 𝑐⃗=−3𝑖ˆ+𝑗ˆ+4𝑘ˆ First find 𝑏⃗×𝑐⃗: 𝑏⃗×𝑐⃗=∣𝑖ˆ𝑗ˆ𝑘ˆ13−2−314∣ =𝑖ˆ(12+2)−𝑗ˆ(4−6)+𝑘ˆ(1+9) =14𝑖ˆ+2𝑗ˆ+10𝑘ˆ Now, |𝑏⃗×𝑐⃗|=√142+22+102 =√196+4+100 =√300=10√3 Next, 𝑎⃗⋅(𝑏⃗×𝑐⃗)=(−2)(14)+5(2)+3(10) =−28+10+30=12 So the volume is 12 Hence the altitude is 1210√3 =65√3 Rationalising, 65√3×√3√3=6√315=2√35 So the altitude is 2√35 Correct option: A.
Q 42MathematicsSection A • MCQ3d geometry+2 / -0The vector equation of the plane passing through the point 𝐴(−2,7,5) and parallel to the vectors 4𝑖ˆ−𝑗ˆ+3𝑘ˆ and 𝑖ˆ+𝑗ˆ+𝑘ˆ is ...𝑟¯⋅(−2𝑖ˆ+7𝑗ˆ+5𝑘ˆ)=26Incorrect𝑟¯⋅(4𝑖ˆ−𝑗ˆ+3𝑘ˆ)=27Incorrect𝑟¯⋅(4𝑖ˆ−𝑗ˆ+5𝑘ˆ)=26Incorrect𝑟¯⋅(−4𝑖ˆ−𝑗ˆ+5𝑘ˆ)=26IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (D)Step-by-Step Solution:The plane is parallel to the two vectors 𝑎⃗=4𝑖ˆ−𝑗ˆ+3𝑘ˆ and 𝑏⃗=𝑖ˆ+𝑗ˆ+𝑘ˆ A plane parallel to two given non-parallel vectors has its normal vector perpendicular to both of them. So the normal vector is given by 𝑛⃗=𝑎⃗×𝑏⃗ Now, 𝑎⃗×𝑏⃗=∣𝑖ˆ𝑗ˆ𝑘ˆ4−13111∣ =𝑖ˆ((−1)(1)−3(1))−𝑗ˆ(4(1)−3(1))+𝑘ˆ(4(1)−(−1)(1)) =−4𝑖ˆ−𝑗ˆ+5𝑘ˆ So the normal vector of the plane is 𝑛⃗=−4𝑖ˆ−𝑗ˆ+5𝑘ˆ The plane passes through 𝐴(−2,7,5), so its position vector is 𝑎0⃗=−2𝑖ˆ+7𝑗ˆ+5𝑘ˆ The vector equation of a plane is 𝑟⃗⋅𝑛⃗=𝑎0⃗⋅𝑛⃗ Now, 𝑎0⃗⋅𝑛⃗=(−2)(−4)+7(−1)+5(5) =8−7+25=26 Hence the equation of the plane is 𝑟⃗⋅(−4𝑖ˆ−𝑗ˆ+5𝑘ˆ)=26 So the correct option is Option D
Q 43MathematicsSection A • MCQ3d geometry+2 / -0The point of intersection of the two lines 𝑥−33=𝑦−3−1,𝑧−1=0 and 𝑥−62=𝑧−13,𝑦−2=0 is....(0,0,0)Incorrect(1,2,6)Incorrect(3,−1,0)Incorrect(6,2,1)IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (D)Step-by-Step Solution:For the first line, 𝑥−33=𝑦−3−1,𝑧−1=0 Take 𝑥−33=𝑦−3−1=𝑡 Then, 𝑥=3+3𝑡,𝑦=3−𝑡,𝑧=1 So any point on the first line is (3+3𝑡, 3−𝑡, 1) For the second line, 𝑥−62=𝑧−13,𝑦−2=0 Take 𝑥−62=𝑧−13=𝑠 Then, 𝑥=6+2𝑠,𝑧=1+3𝑠,𝑦=2 So any point on the second line is (6+2𝑠, 2, 1+3𝑠) At the point of intersection, the coordinates must be the same. From the first line, 𝑧=1. So on the second line, 1+3𝑠=1 3𝑠=0 𝑠=0 Then the point on the second line is (6+2(0), 2, 1+3(0))=(6, 2, 1) So the point of intersection is (6, 2, 1) Correct option: D.
Q 44MathematicsSection A • MCQ3d geometry+2 / -0If the centroid of a tetrahedron 𝑂𝐴𝐵𝐶 is (1,2,−1), where O is the origin, 𝐴(𝑎,2,3),𝐵(1,𝑏,2),𝐶(2,1,𝑐) are the other vertices, then the distance of the point 𝑃(𝑎,𝑏,𝑐) from the origin is...42 unitsIncorrect√107 unitsIncorrect25 unitsIncorrect15 unitsIncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (B)Step-by-Step Solution:The centroid of a tetrahedron is the average of the coordinates of its four vertices. Here the vertices are 𝑂(0,0,0),𝐴(𝑎,2,3),𝐵(1,𝑏,2),𝐶(2,1,𝑐) The centroid is given as (1,2,−1). So, (0+𝑎+1+24,0+2+𝑏+14,0+3+2+𝑐4)=(1,2,−1) Comparing coordinates, 𝑎+34=1 𝑎+3=4 𝑎=1 Now, 𝑏+34=2 𝑏+3=8 𝑏=5 And, 𝑐+54=−1 𝑐+5=−4 𝑐=−9 So, 𝑃(𝑎,𝑏,𝑐)=𝑃(1,5,−9) Distance of 𝑃 from the origin is 𝑂𝑃=√12+52+(−9)2 𝑂𝑃=√1+25+81 𝑂𝑃=√107 So the correct option is √107 units Option B.
Q 45MathematicsSection A • MCQ3d geometry+2 / -0If the lines 𝑥−12=𝑦+13=𝑧−14 and 𝑥−31=𝑦−𝑐2=𝑧1 intersect, then the radius of circle 𝑥2+𝑦2−4𝑥+10𝑦+𝑐=0 is9√2Incorrect92Incorrect7√2Incorrect72IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (C)Step-by-Step Solution:For the first line, 𝑥−12=𝑦+13=𝑧−14=𝜆 So, 𝑥=1+2𝜆,𝑦=−1+3𝜆,𝑧=1+4𝜆 For the second line, 𝑥−31=𝑦−𝑐2=𝑧1=𝜇 So, 𝑥=3+𝜇,𝑦=𝑐+2𝜇,𝑧=𝜇 Since the lines intersect, their coordinates must be equal at the point of intersection. From 𝑥-coordinates, 1+2𝜆=3+𝜇 So, 𝜇=2𝜆−2 From 𝑧-coordinates, 1+4𝜆=𝜇 Equating both values of 𝜇, 2𝜆−2=1+4𝜆 −3=2𝜆 𝜆=−32 Now, 𝜇=1+4(−32) 𝜇=1−6=−5 Now use the 𝑦-coordinates: −1+3𝜆=𝑐+2𝜇 Substitute 𝜆=−32 and 𝜇=−5: −1+3(−32)=𝑐+2(−5) −1−92=𝑐−10 −112=𝑐−10 𝑐=92 Now the circle is 𝑥2+𝑦2−4𝑥+10𝑦+𝑐=0 Substitute 𝑐=92: 𝑥2+𝑦2−4𝑥+10𝑦+92=0 Complete the squares: 𝑥2−4𝑥=(𝑥−2)2−4 𝑦2+10𝑦=(𝑦+5)2−25 So, (𝑥−2)2−4+(𝑦+5)2−25+92=0 (𝑥−2)2+(𝑦+5)2=29−92 (𝑥−2)2+(𝑦+5)2=492 Hence, 𝑟2=492 𝑟=7√2 So the correct option is 7√2 Option C.
Q 46MathematicsSection A • MCQlinear programming+2 / -0The corner points of the feasible region determined by a system of linear constraints are (0,3),(1,1) and (3,0). If the objective function is 𝑧=𝑝𝑥+𝑞𝑦, where 𝑝,𝑞>0, then the condition on p and q such that the minimum of z occurs at both (3,0) and (1,1) is _____𝑝=3𝑞Incorrect3𝑝=𝑞Incorrect𝑝=𝑞2Incorrect𝑝=2𝑞IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (C)Step-by-Step Solution:For the minimum of 𝑧=𝑝𝑥+𝑞𝑦 to occur at both (3,0) and (1,1), the value of 𝑧 at these two corner points must be equal. At (3,0), 𝑧=𝑝(3)+𝑞(0)=3𝑝 At (1,1), 𝑧=𝑝(1)+𝑞(1)=𝑝+𝑞 Since the minimum occurs at both points, 3𝑝=𝑝+𝑞 So, 2𝑝=𝑞 Hence, 𝑝=𝑞2 Now check the third point (0,3): 𝑧=𝑝(0)+𝑞(3)=3𝑞 Using 𝑞=2𝑝, 3𝑞=6𝑝 The value at (3,0) and (1,1) is 3𝑝, which is less than 6𝑝, since 𝑝>0. So the required condition is 𝑝=𝑞2 Correct option: Option C.
Q 47MathematicsSection A • MCQprobability+2 / -0If 𝑋∼𝐵(𝑛,𝑝), then the value of 𝑃(𝑋=𝑘)𝑃(𝑋=𝑘−1) is(𝑛−𝑘𝑘)𝑝𝑞Incorrect(𝑛−𝑘+1𝑘)𝑝𝑞Incorrect(𝑛−𝑘𝑘−1)𝑝𝑞Incorrect(𝑛−𝑘+1𝑘−1)𝑝𝑞IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (B)Step-by-Step Solution:For a binomial random variable 𝑋∼𝐵(𝑛,𝑝), 𝑃(𝑋=𝑘)=𝑛𝐶𝑘𝑝𝑘𝑞𝑛−𝑘 and 𝑃(𝑋=𝑘−1)=𝑛𝐶𝑘−1𝑝𝑘−1𝑞𝑛−𝑘+1 where 𝑞=1−𝑝. Now, 𝑃(𝑋=𝑘)𝑃(𝑋=𝑘−1)=𝑛𝐶𝑘𝑝𝑘𝑞𝑛−𝑘𝑛𝐶𝑘−1𝑝𝑘−1𝑞𝑛−𝑘+1 Separate the terms: =𝑛𝐶𝑘𝑛𝐶𝑘−1⋅𝑝𝑘𝑝𝑘−1⋅𝑞𝑛−𝑘𝑞𝑛−𝑘+1 Now, 𝑝𝑘𝑝𝑘−1=𝑝 and 𝑞𝑛−𝑘𝑞𝑛−𝑘+1=1𝑞 Also, 𝑛𝐶𝑘𝑛𝐶𝑘−1=𝑛−𝑘+1𝑘 So, 𝑃(𝑋=𝑘)𝑃(𝑋=𝑘−1)=(𝑛−𝑘+1𝑘)𝑝𝑞 Hence, the correct option is Option B
Q 48MathematicsSection A • MCQprobability+2 / -0A player tosses two fair coins, he wins Rs. 5 if two heads appear, Rs. 3 if one head appears and Rs. 2 if no head appears, then the variance of the winning amount is1.1875Incorrect1.8175Incorrect1.1785Incorrect1.8157IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (A)Step-by-Step Solution:The possible outcomes when two fair coins are tossed are: 𝐻𝐻, 𝐻𝑇, 𝑇𝐻, 𝑇𝑇 Each outcome has probability 14. The winning amount 𝑋 is: 𝑋=5 when two heads appear: 𝐻𝐻 𝑋=3 when one head appears: 𝐻𝑇,𝑇𝐻 𝑋=2 when no head appears: 𝑇𝑇 So the probability distribution is: 𝑃(𝑋=5)=14,𝑃(𝑋=3)=24=12,𝑃(𝑋=2)=14 Mean of 𝑋: 𝐸(𝑋)=5(14)+3(12)+2(14) 𝐸(𝑋)=54+32+24 𝐸(𝑋)=54+64+24=134 Now, 𝐸(𝑋2)=52(14)+32(12)+22(14) 𝐸(𝑋2)=25(14)+9(12)+4(14) 𝐸(𝑋2)=254+92+44 𝐸(𝑋2)=254+184+44=474 Variance is: Var(𝑋)=𝐸(𝑋2)−[𝐸(𝑋)]2 Var(𝑋)=474−(134)2 Var(𝑋)=474−16916 Var(𝑋)=188−16916=1916 Var(𝑋)=1.1875 So the correct option is: Option A 1.1875
Q 49MathematicsSection A • MCQprobability+2 / -0The probability mass function of a random variable X is given by𝑃(𝑋=𝑥)=5𝐶𝑥25, for 𝑥=0,1,2,3,4,5 and =0, otherwise.Then which of the following is correct?𝑝(𝑥≤2)=𝑝(𝑥≥3)Incorrect𝑝(𝑥≤2)>𝑝(𝑥≥3)Incorrect𝑝(𝑥≤2)<𝑝(𝑥≥3)Incorrect𝑝(𝑥≤2)=2𝑝(𝑥≥3)IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (A)Step-by-Step Solution:Given 𝑃(𝑋=𝑥)=5𝐶𝑥25,𝑥=0,1,2,3,4,5 We need to compare 𝑃(𝑋≤2) and 𝑃(𝑋≥3). First, 𝑃(𝑋≤2)=𝑃(𝑋=0)+𝑃(𝑋=1)+𝑃(𝑋=2) =5𝐶0+5𝐶1+5𝐶225 Using values, 5𝐶0=1,5𝐶1=5,5𝐶2=10 So, 𝑃(𝑋≤2)=1+5+1032=1632=12 Now, 𝑃(𝑋≥3)=𝑃(𝑋=3)+𝑃(𝑋=4)+𝑃(𝑋=5) =5𝐶3+5𝐶4+5𝐶525 Using values, 5𝐶3=10,5𝐶4=5,5𝐶5=1 So, 𝑃(𝑋≥3)=10+5+132=1632=12 Hence, 𝑃(𝑋≤2)=𝑃(𝑋≥3) So the correct option is: Option A
Q 50MathematicsSection A • MCQprobability+2 / -0If events A and B are such that 𝑃(𝐴)=14, 𝑃(𝐴∩𝐵)=110 and 𝑃(𝐴/𝐵)=2𝑃(𝐵/𝐴) then 𝑃(𝐵)=...........12Incorrect15Incorrect18Incorrect25IncorrectView Answer & Detailed SolutionPractice TestOfficial Correct Answer:Option (C)Step-by-Step Solution:Given, 𝑃(𝐴)=14,𝑃(𝐴∩𝐵)=110 We know that 𝑃(𝐵/𝐴)=𝑃(𝐴∩𝐵)𝑃(𝐴) So, 𝑃(𝐵/𝐴)=11014 𝑃(𝐵/𝐴)=110×4=25 Now it is given that 𝑃(𝐴/𝐵)=2𝑃(𝐵/𝐴) So, 𝑃(𝐴/𝐵)=2×25=45 Also, 𝑃(𝐴/𝐵)=𝑃(𝐴∩𝐵)𝑃(𝐵) Hence, 45=110𝑃(𝐵) Now solve for 𝑃(𝐵): 𝑃(𝐵)=11045 𝑃(𝐵)=110×54=18 So, 𝑃(𝐵)=18 Correct option: Option C.