If y = ax . b2x - 1, then d2ydx2 is : from Mathematics

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 Multiple Choice QuestionsMultiple Choice Questions

161.

If y = 2x . 32x - 1, then d2ydx2 is equal to :

  • log2log3

  • log18

  • log182y2

  • log18y


162.

If y = x + x2 + x3 + ... to  where x < 1, then for y < 1dxdy is equal to :

  • y + y2 + y3 + ... to 

  • 1 - y + y2 - y3 + ... to 

  • 1 - 2y + 3y- ... to 

  • 1 + 2y + 3y2 + ... to 


163.

If y = sinx + sinx + sinx + ... , then dydx is equal to :

  • cosx2y - 1

  • - cosx2y - 1

  • sinx1 - 2y

  • - sinx1 - 2y


164.

Given f(0) = 0 and f(x) = 11 - e- 1x for x  0. Then only one of the following statements on f (x) is true. That is f(x), is :

  • continuous at x = 0

  • not continuous at x = 0

  • both continuous and differentiable at x = 0

  • not defined at x = 0


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165.

The value of f at x = 0 so that function fx = 2x - 2- xx, x  0.  is continuous at x = 0, is :

  • 0

  • log(2)

  • 4

  • log(4)


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166.

If y = ax . b2x - 1, then d2ydx2 is :

  • y2 . logab2

  • y . logab2

  • y2

  • y . logab22


D.

y . logab22

    y = axb2x - 1Taking log on both sides, we get logy = xloga + 2x - 1logbOn differentiating w.r.t. x, we get1ydydx = loga + logb2   dydx = ylogab2Again differentiating, we getd2ydx2 = dydxlogab2 = ylogab22


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167.

The value of ddxtan-1x3 - x1 - 3x is

  • 121 + xx

  • 321 + xx

  • 21 + xx

  • 321 + xx


168.

The derivative of y = (1 - x)(2 - x) ... (n - x) at x = 1 is equal to :

  • 0

  • (- 1)(n - 1)!

  • n! - 1

  • (- 1)n - 1(n - 1)!


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169.

Let f(x + y) = f(x)f(y) and f(x) = 1 + sin(3x) g(x), where g(x) is continuous, then f'(x) is : 

  • f(x)g(0)

  • 3g(0)

  • f(x)cos3x

  • 3f(x)g(0)


170.

Let f be continuous on [1, 5] and differentiable in (1, 5). If f (1) = - 3 and f'(x) 9 for all x  (1, 5), then

  • f5  33

  • f5  36

  • f5  36

  • f5  9


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