f(x)=x^3(x^(4)-8)
Find f '(x) by multiplying out before taking the derivative
Is the answer x^12+-8+x^12-8x^3
simplified to 2x^12-8x^3+-16
first, multiply it out..
f(x)=x^12 -8x^3
Now take the derivative. No way is it equal to what you have.