Subject

Mathematics

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

41.

Let Xnz = x + iy : z2  1n for all integers n  1. Then, n = 1 Xn is

  • a singleton set

  • not a finite set

  • an empty set

  • a finite set with more than one element


42.

The equation of hyperbola whose coordinates of the foci are (± 8, 0) and the length of latusrectum is 24 units, is

  • 3x2 - y2 = 48

  • 4x2 - y2 = 48

  • x2 - 3y2 = 48

  • x2 - 4y2 = 48


43.

cos2π7 + cos4π7 + cos6π7

  • is equal to zero

  • lies between 0 and 3

  • is a negative number

  • lies between 3 and 6


44.

The minimum value of 2sinx + 2cosx is

  • 21 - 1/2

  • 21 + 1/2

  • 22

  • 2


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45.

Let α, β denote the cube roots of unity other than 1 and α  β. Let S = n = 0302- 1nαβn. Then, the value of S is

  • either - 2w or - 2w2

  • either - 2w or 2w2

  • either 2w or - 2w2

  • either 2w or 2w2


A.

either - 2w or - 2w2

Case I Let α = w and β = w2 S = n = 0302- 1nww2n       =n = 0302 - 1n w2n      = 1 - w2 + w4 - w6 + w8 - w10 + w12              + ... + w600 - w602 + w604      = 1 - w2 + w - 1 +  w2 + w - 1 + ...            + 1 -  w2 + w      = 0 + ... + 1 - w2 + w      = - w2 - w2        1 + w + w2 = 0      = - 2w2

Case II Let α = w2 and β = w S = n = 0302- 1n w2wn        = n = 0302- 1n w4w3n        = n = 0302- 1nw       = 1 - w + w2 - w3 + w4 - w5 + w6 - ...               + w300 - w301 + w302      = 1 - w + w2 - 1 + w - w2 + 1 - 1 ...               + 1 - w + w2      = 0 + ... + 1 + w2 - w      = - w - w = - 2w


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46.

Let tn denotes the nth term of the infinite series 11! + 102! + 213! + 344! + 495! +... . Then, limntn is

  • e

  • 0

  • e2

  • 1


47.

A poker hand consists of 5 cards drawn at random from a well-shuffled pack of 52 cards. Then, the probability that a poker hand consists of a pair and a triple of equal face values (for example, 2 sevens and 3 kings or 2 aces and 3 queens, etc.) is

  • 64165

  • 234165

  • 17974165

  • 14165


48.

If the circle x2 + y2 + 2gx + 2fy + c = 0 cuts the three circles x2 + y2 - 5 = 0, x2 + y2 - 8x - 6y + 10 = 0 and x2 + y2 - 4x + 2y - 2 = 0 at the extremities of  their diameters, then

  • c = - 5

  • fg = 147/25

  • g + 2f = c + 2

  • 4f = 3g


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49.

Let f(x) be a differentiable function in [2, 7]. If f(2) = 3 and f'(x)  5 for all x in (2, 7), then the maximum possible value of f(x) at x = 7 is

  • 7

  • 15

  • 28

  • 14


50.

If sin-1x13 + csc-11312 = π2, then the value of x is

  • 5

  • 4

  • 12

  • 11


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