00:01
So what we have to do in this problem is factor the denominator.
00:07
So i'm looking at that x squared minus 4x minus 5.
00:10
I'm going to go ahead and rewrite it as x minus 5 and then x plus 1.
00:16
That should work for us.
00:19
And so as i'm, actually i probably should have left it the way it was, 7 minus x over what i say, x squared minus 4x minus 5.
00:29
Because if you're trying to find where we are increasing or decreasing, you'd want to know the derivative of that.
00:39
So a few things i do want to point out though is that x cannot equal 5 or negative 1.
00:44
That's kind of why i do that work.
00:47
So then we're going to do the derivative where the derivative of the top would be negative 1.
00:51
We leave the bottom alone.
00:55
And then minus the derivative of the bottom which is 2x minus 4.
01:00
Leave the top alone.
01:01
And then all over the denominator squared which is just reiterating that you have those domain restrictions.
01:11
But what i would do next is see where the numerator equals zero.
01:14
So i'm going to distribute that negative x plus 5.
01:19
And here i'm going to distribute, what do i end up with? a negative 2x squared and then a 14x with a 4x.
01:34
So that's 18x.
01:37
And then negative 4 times 7 should be negative 28...