The function f(x) = x3 + 3x decreases in the inter

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 Multiple Choice QuestionsMultiple Choice Questions

691.

If a ball is thrown vertically upwards and the height 's' reached in time 't' is given by s = 22t - 11t2, then the total distance travelled by the ball is

  • 44 units

  • 33 units

  • 11 units

  • 22 units


692.

The sum of two positive numbers is given. If the sum of their cubes is minimum, then

  • they are equal

  • one is twice the other

  • they are unequal

  • one is thrice the other


693.

The perimeter of a sectoris a constant. Ifits area is to be maximum, then the sectorial angle is

  • πc6

  • πc4

  • 4c

  • 2c


694.

The tangent to the curve xy = 25 at any point on it cuts the coordinate axes at A and B, then the area of the OAB is

  • 50 sq units

  • 25 sq units

  • 75 sq units

  • 100 sq units


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695.

The length of the subtangent, ordinate and the subnormal are in

  • AP

  • HP

  • GP

  • Arithmetico-geometric progression


696.

The maximum value of xe-x is

  • e

  • 1e

  • - e

  • 1e


697.

The maximum area of a rectangle that can be inscribed in a circle of radius 2 units is

  • 8π sq units

  • 4 sq units

  • 5 sq units

  • 8 sq units


698.

If the length of the subtangent at any point to the curve xyn = a is proportional to the abscissa, then n is

  • any non-zero real number

  • 2

  • - 2

  • 1


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699.

The function f(x) = x3 + 3x decreases in the interval

  • (- 3, 3)

  • - , 3

  • 3, 

  • (- 9, 9)


A.

(- 3, 3)

Given, fx = x3 + 3xOn differentiating w.r.t. x, we get        f'x = 13 - 3x2Since, function is decreasingi.e.,       f'x < 0 13 - 3x2 < 0          13 < 3x2         x2 < 9          x  - 3, 3

which is the required interval in which function f(x) decreases.


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700.

The tangent to the curve y = x3 + 1 at (1, 2) makes an angle θ with y-axis, then the value of tanθ is

  • - 13

  • 3

  • - 3

  • 13


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