This is the new one! Please help I’m so lost

(a) (f o g)(x) =  x^2 - 15x + 54

(b) (g o f)(x) = x^2 + 3x - 9

(c) (f o f)(x) = x^4 + 6x^3 + 12x^2 + 9x

(d) (g o g)(x) = x - 18

Step-by-step explanation:

f(x) = x^2 + 3x

g(x) = x - 9

(a)

(f o g)(x) = f(g(x)) = (g(x))^2 + 3(g(x)) = (x - 9)^2 + 3(x - 9)

(f o g)(x) = x^2 - 18x + 81 + 3x - 27

(f o g)(x) = x^2 - 15x + 54

(b)

(g o f)(x) = g(f(x)) = f(x) - 9 = x^2 + 3x - 9

(c)

(f o f)(x) = f(f(x)) = (x^2 + 3x)^2 + 3(x^2 + 3x)

(f o f)(x) = x^4 + 6x^3 + 9x^2 + 3x^2 + 9x

(f o f)(x) = x^4 + 6x^3 + 12x^2 + 9x

(d)

(g o g)(x) = g(g(x)) = x - 9 - 9 = x - 18