00:01
Okay, the derivative is given, so just set it to zero and we'll see that x equals 2 and x equals 1 are the critical numbers.
00:09
So, apply the first derivative test.
00:16
So, we don't know much about the function, but we know this part, this much.
00:22
So, let's put some values.
00:24
If x equals zero, negative 2 squared is positive negative.
00:28
And 3 over 2, that's positive positive.
00:34
And put 2, positive positive, right? i mean, put something 3, positive positive.
00:41
Okay, so we have a minimum, no maximum.
00:47
So, this is local minimum here, because the function decreasing and then increasing.
00:55
So, that means it's a minimum.
00:57
So, at local minimum, x equals 1, no max.
01:01
And the second derivative, let's take the derivative of the first derivative, 2x minus 2 times x minus 1, plus the derivative of x minus 1 is 1x minus 2 squared.
01:18
Set it to zero.
01:20
As you see, x minus 2 is common.
01:24
So, we have 2x minus 2 here and then plus x minus 2 here.
01:30
And we get x minus 2, 3x minus 4.
01:37
Okay, so x equals 2 and x equals 4 over 3...