00:01
In this problem, we're asked to evaluate the inverse is derivative at the, in this case, the c value is 8.
00:10
So i'm going to do some work here to, i guess, just see if the function even is one -to -one.
00:19
They ask you to check that.
00:23
And what you need to do, i'm going to rewrite this square root of x.
00:27
How about this? i'll write it fine there.
00:29
But i'm going to rewrite it as 2x to the 1 half power.
00:33
So to show that something has an inverse, you just have to show it's increasing or decreasing the entire time.
00:38
Well, the derivative of this would be 1, and then doing the power rule, half of 2 is 1, x to the negative 1⁄2 power.
00:46
And the reason why this is always positive and is always increasing is because we can only plug in positive numbers for x anyway.
01:02
So if you take a positive and add a positive to it, you have to get a positive.
01:09
So it is one -to -one.
01:11
It is always increasing because the derivative is always positive.
01:15
So the next thing i like to do is to guess and check...