00:01
We wish to find the absolute and local extrema for the following function.
00:05
I am going to rewrite that as x minus 4x to the one -half power.
00:12
And there are limitations on the x value because you can only take the square root of values that are non -negative.
00:21
So the x domain is that x values are greater than equal as zero.
00:27
Let's look at our critical numbers.
00:30
The derivative is 1 minus 2 x to the negative 1 half, or 1 minus 2 over the square of x.
00:42
It is non -differentiable at x equals 0.
00:47
However, that's on the border of the domain.
00:52
So it's not going to be any direction change there, but it is nevertheless a critical number.
01:00
The other critical numbers could occur if the derivative is equal to zero.
01:06
To solve that, i could subtract the one, multiply both sides by the square root of x.
01:14
To give me negative 2 equals negative square root of x, multiply both sides by negative 1.
01:23
So i have square to 2 or 2 equals square of x, and squaring the x gives me x equals 4.
01:29
So we do have two critical numbers...