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Consider the function f(x)=−2x3+3x2+36x−15f(x) = -2x^3 + 3x^2 + 36x - 15, then which of the following are TRUE?

A. f(x)f(x) increases on (−2,3)(-2, 3)

B. f(x)f(x) decreases on (−∞,−2)∪(3,∞)(-\infty, -2) \cup (3, \infty)

C. f(x)f(x) increases on (−∞,−2)∪(3,∞)(-\infty, -2) \cup (3, \infty)

D. f(x)f(x) neither increases nor decreases on (−2,3)(-2, 3)

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 1

f′(x)=−6x2+6x+36=−6(x−3)(x+2)f'(x) = -6x^2 + 6x + 36 = -6(x-3)(x+2).

This is positive exactly when −2<x<3-2 < x < 3, so ff increases on (−2,3)(-2,3) and decreases on (−∞,−2)(-\infty,-2) and (3,∞)(3,\infty). Hence A and B are true, C and D are false.

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