1. finding a tangent line.......

So i can't figure out the following:

f(x) = 2x^3 - 3x^2 - 72x + 6 ....for what values of x does this graph have a horizontal tangent...i think there are supposed to be two values

2. Originally Posted by frozenflames
So i can't figure out the following:

f(x) = 2x^3 - 3x^2 - 72x + 6 ....for what values of x does this graph have a horizontal tangent...i think there are supposed to be two values
set $f'(x) = 0$ and solve for x.