Find the value of x for which the function f x ... - JAMB Mathematics 2007 Question

f(x) = 2x³ - x² - 4x – 4

f’(x) = 6x² - 2x – 4

As f’(x) = 0

Implies 6x² - 2x – 4 = 0

3x – x – 2 = 0 (By dividing by 2)

(3x – 2)(x + 1) = 0

3x – 2 = 0 implies x = -²/₃

Or x + 1 = 0 implies x = -1

f’(x) = 6x² - 2x – 4

f’’(x) = 12x – 2

At max point f’’(x) < 0

∴f’’(x) = 12x – 2 at x = -1

= 12(-1) – 2

= -12 – 2 = -14

∴Max at x = 1