Answer:
8(2x+5)^3 - 28(2x+5) + 61 OR 64x^3 + 480x^2 + 1144x + 921
Step-by-step explanation:
I believe you are trying to find f(g(x)). To do this, you must insert g(x) in the place of x in the function.
f(g(x)) = 8(2x+5)^3 - 28(2x+5) + 61
Then, if you don't want to leave this as your answer and simplify, multiply and foil out to get:
64x^3 + 480x^2 + 1144x + 921
Edit: After looking at it, the question might be f(x)/g(x). In that case, use long division with f(x) on the inside and g(x) on the outside. Otherwise, use the answer above.