Answer:x^8+7x^4
Step-by-step explanation:
First we have to do the g(x) cause it's closest to x.
g(x)=x^4
x^4 is the output for g(x) ad input for f(x). So now we have to put it in x's place in here➡️f(x)
So, f(x^4)=(x^4)^2+ 7(x^4)
=x^8+7x^4
It's the final output
