Solution:Let f : (-1,1) → R be a differentiable function with f(0)= - 1 and f ' (0) = 1
h(x) = f(2f (n) + 2
Differentiate both side w.r.t x
h' (x) = f '(2f(x) + 2) 2 f' (x)
h' 0 = f ' (2f(0) + 2) . 2f ' (0) = f ' (-2 + 2). 2 (1)
= f ' (0). 2 = (1). 2 = 2[ f(0) = -1 and f '(0) = 1]