1.

f(x) = (x+1)3(x - 3)3 is increasing inA. (-∞, 1)B. (-1, 3)C. (3, ∞)D. (1, ∞)

Answer»

Answer is : D. (1, ∞)

Given:

⇒ f(x) = (x+1)3.(x - 3)3

⇒ f’(x) = 3(x+1)2(x - 3)3 + 3(x - 3)3 (x+1)3

Put f’(x) = 0

⇒ 3(x+1)2(x - 3)3 = -3(x - 3)2(x+1)3

⇒ x - 3 = -(x+1)

⇒ 2x = 2

⇒ x = 1

When x>1 the function is increasing.

x<1 function is decreasing.

So, f(x) is increasing in (1, ∞).


Discussion

No Comment Found

Related InterviewSolutions