The values of for which the function decreases monotonically throughout for all real

MATHEMATICS · Single correct · A Level · Mathematics · Differentiation · Differentiation

Problem

The values of

a

for which the function

(a + 2)x^3 - 3ax^2 + 9ax - 1

decreases monotonically throughout for all real

x

, are (a)

a < -2

(b)

a > -2

(c)

-3 < a < 0

(d)

-\infty < a \leq -3