The function x5 - 5x4 + 5x3 - 1 is from Mathematics Application

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 Multiple Choice QuestionsMultiple Choice Questions

641.

On which of the following intervals is the function f(x) = 2x2 - logx, x  0 increasing 2.

  • 12, 

  • - , - 12  12, 

  • - , - 12  0, 12

  • - 12, 0  12, 


642.

The length of the normal to the curve x = aθ + sinθ, y =  a1 - cosθ at θ = π2 is

  • 2a

  • a2

  • a2

  • 2a


643.

The maximum value of logxx is

  • e

  • 2e

  • 1e

  • 2e


644.

The smallest circle with centre on y-axis and passing through the point (7, 3) has radius

  • 58

  • 7

  • 3

  • 4


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645.

If sum of two numbers is 6, the minimum value of the sum of their reciprocals is

  • 65

  • 34

  • 23

  • 12


646.

The normal to the curve x = acosθ + sinθ, y = asinθ - θcosθ at any point θ is such that

  • it makes a constant angle with x-axis

  • it passes through origin

  • it is at a constant distance from origin

  • None of the above


647.

The function f(x) = log1 + x - 2x2 + x is increasing on

  • - 1, 

  • - , 0

  • - , 

  • None of these


648.

The minimum value of x2 + 11 + x2 is at

  • x = 0

  • x = 1

  • x = 4

  • x = 3


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649.

The maximum value of 3 cosθ + 4 sinθ is

  • 3

  • 4

  • 5

  • None of these


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650.

The function x5 - 5x4 + 5x3 - 1 is

  • neither maximum nor minimum at x = 0

  • maximum at x = 0

  • maximum at x = 1 and minimum at x = 3

  • minimum at x = 0


C.

maximum at x = 1 and minimum at x = 3

Let fx = x5 - 5x4 + 5x3 - 1On differentiating w.r.t. x, we get     f'x = 5x4 - 20x3 + 15x2For maximum or minimum, put f'(x) = 0      5x4 - 20x3 + 15x2 = 0 x25x2 - 20x + 15 = 0    5x2x - 1x - 3 = 0         x = 0,1, 3Again differentiating w.r.t. x, we getf''x = 54x3 - 12x2 + 6xAt x = 1, f''1 = 54 - 12 + 6         = - 10 < 0, maximumAt x = 3, f''3 = 54 × 27 - 12 × 9 + 6 × 3        = 90 > 0, minimumAt x = 0, f''0 = 50 - 12 × 0 + 6 × 0 = 0,we have further check     f'''x = 512x2 - 24x + 6 f'''0 = 30  0       Inflexion fx is maximum at x = 1 and minimum at x = 3.


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