00:01
So we're given the linear function, f of x is equal to mx plus b.
00:05
And m and b can be any numbers.
00:07
So we first need to show that f of x is one to one.
00:12
And to do that, let's assume that for x1 and x2, that are real numbers, let's say f of x1 is equal to f of x of 2.
00:25
So by definition, m times x1 plus b is equal to m x2 plus b.
00:36
So you can subtract both sides by b gives m x1 is equal to mx2.
00:43
We divide both sides by m.
00:46
Now this does assume that m is not equal to zero.
00:52
Now we get x1 is equal to x2.
00:55
And then we're done.
00:55
By definition, when two inputs have the same output, they have to be the same.
01:03
And that's the definition of one to one.
01:05
Now for two, we need to show that ffx has an inverse and write down this inverse.
01:15
So we can go ahead and just solve for the inverse.
01:17
But again, it's really important that f is not equal to zero.
01:21
Otherwise, ffx does not have an inverse.
01:24
Anyway, to solve this, we can reverse the role of y and x...