Question

F(x) = 3x + 9, g(x) = 3x2
Find (fg)(x)

Answer 1

I guess your g(x) = 3x2 should be g(x) = 3x². If so then:

f(x) = 3x + 9, g(x) = 3x²

find f(g(x)) or f(3x²) , that means replace x in f(x) with x = 3x²

f(g(x)) = f(3x²) = 3(3x²) + 9 → f(g(x))= 9x² + 9

Answer 2

This situation wants you to first multiply f by g.=
(i am going to assume it is 3x squared)
6x(cubed)+27x(squared).
Now put in x for the variable, but since it is already done, that is your answer.
6x(cubed)+27x(squared)

Hope this helped!