Composite Function Conundrum

Question

The problems given are:

f(x)=x² -9x and g(x)=x-7

I already found (f o g)(x) and (g o f)(x). But now I need (f o f)(x) and (g o g)(x)

Answer 1

Those are recursive compositions...

F comp F:

(x^2 - 9x)^2 - 9 (x^2 - 9x) =

x^4 - 18x^3 + 81x^2 - 9x^2 + 81x =

x^4 - 18x^3 + 72x^2 + 81x

G comp G:

x-7 - 7 = x-14