Inverse f(x)

1. Jul 11, 2007

luznyr

1. The problem statement, all variables and given/known data

Find inverse of f(x) when f(x) = (2x-5)/(7x+4)

2. Relevant equations

none

3. The attempt at a solution

x=(2y-5)/(7y+4) and then i get stuck trying to rearrange back to y=...

2. Jul 11, 2007

Dick

Where do you get stuck?? Multiply both sides by 7y+4, move all of the terms with a y in them to one side and solve for y. It's not that hard.

3. Jul 11, 2007

luznyr

ok that gives x(7y+4) -2y= -5, 7xy+4x-2y=-5, so how do i get it back to y= then genius?

4. Jul 11, 2007

danago

Keep all your terms with 'y' in them on one side, and all the other terms on the other, and then take out a factor of 'y', and it should be clear from there.

5. Jul 11, 2007

Dick

So 4x+5=2y-7xy=y(2-7x). Can you solve for y now, genius?

6. Jul 11, 2007

luznyr

haha yep ty

7. Jul 11, 2007

Dick

BTW sorry about the 'it's not that hard' crack. If you don't see it, you don't see it.

8. Jul 11, 2007

luznyr

yeah sry bout the genius thing, thanks for the help anyone, much appreciated