Evaluate the derivative f'(x) at x=0, iff (x) = e4x A Question 6 (1 point) ) Listen Given: y = f(x) To find the value of x where the graph of the function has a horizontal tangent line, we must: O set f'(x) equal to 0 Osubstitute 0 into f'(x) set f(x) equal to O substitute 0 into f(x)