00:01
F inverse prime of 2 for f of x equals the square root of x minus 4.
00:06
Well, f inverse prime of 2 is 1 over f prime of, well, it can't be of 2 unless it's accidental, okay, because 2 is going into f inverse.
00:22
So here's what i'm talking about.
00:25
Here's the domain of f.
00:28
So f takes numbers here and does stuff to them and sends them over here into its range.
00:39
And so then f inverse comes along and takes the same number only from the range and sends it back to the domain.
00:48
If this was x and this was y, f sends x to y and then f inverse sends y back to the same x again.
00:57
So what used to be the range of f is now the domain of f inverse.
01:04
And so f inverse takes it and sends it to its range, which is the domain of f.
01:10
So if you're plugging a number into f inverse, it came from f inverse's domain, which is the range of f, the range of f, which means it is a y value.
01:24
If you're plugging two into f inverse, it's a y value...