Question

Let f (x) = 30 - 2x - x³ then find the number of positive integral values of x which satisfies f (f(f(x))) >  f (f( -x)).

Answer 1

f (x) = − 30 - 2x - x³

f''(x) = −2- 3x² < 0 ⇒ f (x) is decreasing function. Thus,