00:01
So f of x is equal to x cubed minus a x where a is in the positive real numbers and we're going to try and figure out what our critical points are of this function.
00:11
So to do that, we're going to need to find the derivative function f prime of x, which is going to be equal to the derivative of x cubed, which we just use the power rule to find.
00:20
And we bring down the power, so we bring down the three multiplied by x and raise it to the previous power minus one.
00:27
So three minus one is two.
00:29
And we do the same thing here with x to the first.
00:32
So we bring down the 1, we multiply it by a, and then we have x to the 1 minus 1 power, x to the 0th, which is just 1.
00:39
So that means our second derivative here is equal to 3x squared minus a, and we can set our second derivative equal to 0 and solve for a, or sorry, solve for x here.
00:51
So we're going to plus a over.
00:53
We get a is equal to 3x squared.
00:55
We divide both sides by 3...