00:01
In this problem, we have this function, g of x.
00:04
Oops, let me make sure that looks like a g.
00:05
G of x equals the square root of 9 minus x squared.
00:11
Now, we need to find the maximum and minimum values of this function.
00:16
And then grab it.
00:16
Now, the way that we're going to do that is we're going to take the first derivative and then take the second derivative.
00:22
Now, we're going to take the first derivative and make that equal to zero and then find our critical points.
00:28
So the first thing i'm going to do is rewrite this.
00:30
As an exponent, 9 minus x squared to the 1 half.
00:34
Let me show you, looks up a 2, right, to the 1 half, to the 1 half.
00:38
That we don't make that look very nice, can i? there we go.
00:41
Now, i'm going to use the power rule, g of x, and i'm actually going to use the power roll in the chain rule.
00:47
So i'm going to say that this is equal to 1 ,5, 9 minus x squared to the negative 1ā2, and then i'm going to multiply that times the derivative of the inner function, which is going to be negative 2x.
01:02
All right.
01:02
Now, simplifying one half of negative 2 is negative 1.
01:05
So this is going to be negative x.
01:09
I'll say negative x.
01:12
Well, this is how i'll do it first, negative x over the square root of 9 minus x squared.
01:19
Now, i'm doing that because i want to set this equal to zero.
01:22
And that's actually going to be quite easy.
01:24
That means that x is going to equal zero because i have to multiply by 9 minus x squared and i'm also going to find that x is equal to zero.
01:36
So where x equals zero is a critical point.
01:40
Now we also have to think of the domain of this function, right? the domain is anywhere between positive and negative three because we can't take the square root of a negative number and it be in the real numbers.
01:53
So here we also have that x in the domain of this, x is not differentiable where x equals three or negative three because that would mean that we have a denominator of zero.
02:07
So x is not differentiable here at plus or minus three.
02:12
All right.
02:12
No, that's important because those are test points that we need for our minimum and maximum.
02:18
Now, we're going to take the second derivative now.
02:21
So i'm going to keep this as, now i'm going to rewrite this, i just say, in order to make it easier to differentiate.
02:27
So g prime of x is going to equal negative x times 9 minus x squared to the negative 1 half.
02:38
All right.
02:38
Now i'm just going to draw a little dotted line here to separate my answers.
02:42
All right, so that now we're looking here and keep it a little more orderly for us.
02:45
Now, we're going to do the same process.
02:48
We're going to use the power rule and the chain rule...