Find equations for the horizontal and vertical tangent lines to the curves

That's where slope is 0, any line tangent at that point will be horizontal: when x=3 or when x=−1. Then find the corresponding y value in the first equation: f(x)=(x−2)(x2−x−11), to determine the two points: (x1,y1),(x2,y2) where the line tangent to f(x) is horizontal