All the problem is asking you to do is multiply f(x) with g(x). So you multiply x^4-9 with x^3+9
(x^4-9)(x^3+9)=x^7+9x^4-9x^3-81
So the right answer is x^7+9x^4-9x^3-81
Hope this helped! Feel free to message me with more questions and mark brainliest!
