00:01
We are trying to find the absolute extrema for the given function from 1 to 3.
00:07
Let's first locate the critical numbers.
00:11
To take the derivative, we will use the quotient rule.
00:15
Bottom times the derivative of the top, which is 1 over x, minus the top times the derivative of the bottom, which is 1 over the bottom square.
00:25
So we have 1 minus lnx over x squared.
00:31
This does happen to be non -differentiable at zero, but it was discontinuous at that point, and it wouldn't have mattered anyway because that's not in the interval.
00:43
The only critical numbers we could get would be when the fraction is zero.
00:48
And fractions are zero when the top is zero.
00:53
Let's subtract the one, give ourselves negative natural log x equals negative one, multiply both sides by negative one, and then we could take e to each of those powers and say, well, e to the natural log x, by definition, that's x and x equals e.
01:18
E is about 2 .71...