Question 836691
What does r stand for? If r is a constant, then f'(x) = 0. If you meant to say


*[tex \Large f(x) = x^8 - 7x^6 + 3x^2 + 1]


then by applying the power rule,


*[tex \Large f'(x) = 8x^7 - 42x^5 + 6x]