Find (g * f)(x) and (f * g)(x) for the given functions f and g.

Question

f(x) = x3 + 7x, g(x) = -5x

(g * f)(x) =

(f * g)(x) =

the "*" stands for this small "o" looking thing but the symbol for it isn't on the keyboard

Answer 1

f(x) = x³ + 7x, g(x) = 5x

(f o g)(x) = f(g(x)) = f(5x) = (5x)³ + 7(5x) = 125x³ + 35x

(g o f)(x) = g(f(x)) = g(x³ + 7x) = 5(x³ + 7x) = 5x³ + 35x