# How do I find the inverse?

• Feb 16th 2010, 09:24 AM
Henryt999
How do I find the inverse?
Problem is find the inverse of $f(x) = x^2-2x+4$
• Feb 16th 2010, 09:30 AM
Plato
Quote:

Originally Posted by Henryt999
Problem is find the inverse of $f(x) = x^2-2x+4$

The short answer is: you can't.
There must be some restrictions. What are they?
• Feb 16th 2010, 11:11 AM
Henryt999
ops
Quote:

Originally Posted by Plato
The short answer is: you can't.
There must be some restrictions. What are they?

Ops, sorry it said: $f:[1,\infty)\rightarrow R, f(x) = x^2 -2x +4$
• Feb 16th 2010, 11:16 AM
icemanfan
Set $x = y^2 - 2y + 4$

and solve for y.
• Feb 16th 2010, 11:22 AM
Henryt999
Thats it?
Quote:

Originally Posted by icemanfan
Set $x = y^2 - 2y + 4$

and solve for y.

Yes, thanks, that I understand I get
$x-4 = y(y-2)$
And now what?
• Feb 16th 2010, 11:26 AM
icemanfan
Quote:

Originally Posted by Henryt999
Yes, thanks, that I understand I get
$x-4 = y(y-2)$
And now what?

Try this:

$x = y^2 - 2y + 4$

$x = y^2 - 2y + 1 + 3$

$x = (y - 1)^2 + 3$

etc.