Question 841328
{{{f(g)=3(-x^2)-9=-3(x^2+3)}}}
{{{g(f)=-(3x-9)^2=-(9x^2-54x+81)}}}
{{{f(f)=3(3x-9)-9=9x-27-9=9x-36=9(x-4)}}}
{{{g(g)=-(-x^2)^2=-x^4}}}