Question

Let f(x) = -3x2 – 1 and g(x) = -5x. Find f(g(x)).

Answer 1

Substitute g(x) where x is in the definition of f(x).
  f(g(x)) = -3(g(x))^2 - 1
  f(g(x)) = -3(-5x)^2 - 1
  = -3(25x^2) - 1

f(g(x)) = -75x^2 - 1