00:01
Given the function, f, we want to find f of a to begin with.
00:07
You find f of a by plugging a in for x, so it becomes a over a plus 1.
00:13
And then you want to find f of a plus h by plugging a plus h in for x.
00:20
That looks like a plus h over a plus h plus 1.
00:28
Last, you want to find f of a plus h minus f of a plus h.
00:34
All over h.
00:36
We've already done the work for the numerator.
00:39
F of a plus h.
00:44
F of a plus h is a plus h over a plus h plus 1 minus f of a which is a over a plus 1 and then all of that will be over h.
00:57
All right so that would be equal to think of dividing by h is multiplied by 1 over h.
01:07
Okay.
01:09
So 1 over h times over, well, we need a common denominator for subtracting these two fractions.
01:22
And so it would be a plus h times a plus 1 minus a times a plus 1 in order to get our common denominator of the product a plus h plus 1 times a plus 1...