ANSWER
[tex]g(f(x))=7x^2+42x+63[/tex]
EXPLANATION
We want to find the composition:
[tex]g(f(x))[/tex]
To do this, substitute f(x) for x in g(x) and simplify.
That is:
[tex]g(f(x))=7(x+3)^2[/tex]
Simplifying the above function, we have:
[tex]\begin{gathered} g(f(x))=7(x+3)(x+3) \\ g(f(x))=7(x^2+3x+3x+9)=7(x^2+6x+9) \\ g(f(x))=7x^2+42x+63 \end{gathered}[/tex]
That is the answer.
