If ∫xfxdx = fx2, then f(x) is equal to : from

Subject

Mathematics

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

21.

If xx + 1dx = Ax + Btan-1x + c, then :

  • A = 1, B = 1

  • A = 1, B = 2

  • A = 2, B = 2

  • A = 2, B = - 2


22.

x3sintan-1x41 + x8dx is equal to :

  • 14costan-1x4 + c

  • 14sintan-1x4 + c

  • - 14costan-1x4 + c

  • 14sec-1tan-1x4 + c


23.

In0π4tannxdx, then limnnIn + In +2 equals :

  • 12

  • 1

  • zero


24.

A bag contains 3 black, 3 white and 2 red balls. One by one, three balls are drawn without replacement. The probabilitythat the third ball is red is equal to :

  • 256

  • 356

  • 156

  • 1456


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25.

The angle between the line x - 32 = y - 11 = x + 4- 2 and the plane, x + y + z + 5 = 0 is :

  • sin-123

  • sin-113

  • π4

  • sin-1133


26.

A vector perpendicular to 2i^ + j^ + k^ and coplanar with i^ + 2j^ + k^ and i^ + j^ + 2k^ is :

  • 5j^ - k^

  • i^ + 7j^ - k^

  • 5j^ + k^

  • 2i^ - j^ - k^


27.

If a = 2i^ - 3j^ + pk^ and a × b = a = 4i^ + 2j^ - 2k^, then p is :

  • 0

  • - 1

  • 1

  • 2


28.

Let a = i^ - j^, b = j^ - k^, c = k^ - i^. If d is a unit vector such that a . d = 0 = b c d, then d is (are) :

  • ± i^ + j^ - k^3

  • ± i^ + j^ - 2k^6

  • ± i^ + j^ + k^3

  • ± k^


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29.

If xfxdx = fx2, then f(x) is equal to :

  • ex

  • e- x

  • log(x)

  • ex22


D.

ex22

Let us assume fx = ex22x . ex22dx = 2xex24 dxLet     x2 = t 2xdx = dt    et4dt = et4 + c = 12ex22 + c xfxdx = 12fx + c when fx = ex22


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30.

02x2dx is :

  • 2 - 2

  • 2 + 2

  • 2 - 1

  • - 2 - 3 + 5


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