00:01
Find the coordinates of the points on the curve given where the tangent line is horizontal.
00:07
Well, the tangent line is horizontal when its slope equals to zero.
00:12
And in this situation, we can do that where the derivative equals zero.
00:18
So the first thing we're going to do is find the derivative.
00:21
Y prime is going to be 3x squared minus 2x minus 1.
00:27
That's our derivative.
00:28
Now we now want to set that equal to 0.
00:31
3x squared minus 2x minus 1.
00:34
Let's see if this will factor.
00:37
I know we've got to have a 3x and an x, a 1 and a 1.
00:41
I need to get a negative 2x.
00:43
I'll put that as a negative and that is a positive.
00:46
Now where is this going to be equal to 0? well, 3x plus 1 equals 0 means x equals negative 1 3rd...