00:02
Here, we want to find the value of k that's going to make the integral from 0 to k of x over x squared plus 4 equal to 1 half the ln of 4.
00:16
So, let's go ahead and say a u substitution for this integral.
00:21
Say u is equal to x squared plus 4.
00:25
Well, that means that du is going to be 2x dx.
00:29
Now, in this integral, we have x dx.
00:31
We don't have a 2x dx.
00:33
So, let's just put a 2 here.
00:35
But to do that, let's multiply by 1 half, and that makes it so that this 2x dx becomes du.
00:41
So we have 1 half the integral of du over u.
00:48
So this integral then goes from x equals 0, which means u is 4, to x equals k, which means u equals k squared plus 4.
01:01
So the integral of u is ln of absolute value of 2...