find all values of x where tangent line is horizontal

Jul 2015
613
16
United States
f(x)=2x^3+9x^2-60x+4


this polynomial is not factorable.. do I just put no x values as the answer or what should I put


Woops.! My bad. I had to derive this whole equation with the power rule of derivative hehe :D
 
Last edited:

HallsofIvy

MHF Helper
Apr 2005
20,249
7,909
Well, I would use the word "differentiate" rather than "derive" but, yes, the slope of the tangent line to the graph of y= f(x), at x= a, is f'(a). A line is horizontal if and only if that slope is 0: f'(x)= 0. You need to solve f'(x)= 0.