You can
put this solution on YOUR website!
First find (g+f)(x) by adding the right sides of g(x) and f(x).
Then find (g+f)(x/4) by replacing every x in (g+f)(x) by x/4.
[It probably won't, but if replacing every x by x/4 confuses you, then
replace every x first by z, and then replace every z by x/4.]
Edwin