[For Math Geeks!] Inverse Functions

[Mzor203]

I'm having issues with a math worksheet (well, a small part of it anyway). It's due tomorrow and our school is having an issue so no one can sign out textbooks, and the internet doesn't seem to have an answer to my particular problem.

I'm trying to find the inverse of a function. First off, a quick example of this to refresh your memory!

If I had the function y = 2x^2, the inverse would simply be x = 2y^2, or to put it into a better form:

y = (x/2)^1/2

So basically you switch the y and x in the function. This will completely swap the y and x values of its graph.

Now that's no problem. I'm having issue when I come up against something like:

y = ____x____
x + 2



Swapping around the varables means that you end up, once you simplify it a little bit, with something like:

x = ____y____
y + 2



Which goes to:

xy + 2x = y

or

x(y + 2) = y

And then from there it's just... unsolvable for y, I suppose. The only way to get both y's on the same side is to divide both sides by y but that means that the right side simply translates to "1". Which ends up like:

3x = 1

So the y disappeared. Omnom.

I must be missing something here.

EDIT: Chrome like... doesn't have a WYSIWYG editor so excuse the formatting...

[Sith Lord 13]

x = ____y____
y + 2


Going from there you get

xy +2x = y

2x= y - xy

2x = y (1-x)

2x = y
1-x

[Mzor203]

Aha, okay, I see what I was doing wrong then.

All this time for some reason I was going

x(y+2) = xy + 2y instead of xy + 2x.

Thanks for the quick response.

[Sith Lord 13]

Not a problem. Glad I could help. If you need anything clarified, just let me know.

[Mzor203]

The rest of this is easy enough now, it's honestly been a while since I've put some of this algebra to use, the fact that I could subtract a term from both sides of the equation just... didn't register, I guess.

[Sith Lord 13]

The rest of this is easy enough now, it's honestly been a while since I've put some of this algebra to use, the fact that I could subtract a term from both sides of the equation just... didn't register, I guess.

I've done the same thing. Math is like anything. You don't use it, you loose it. :)

[Magus]

x(y+2) = xy + 2y instead of xy + 2x.


That's because you didn't multiply "X" with each term. I have this little trick were I usually put a curve(up or down) to know which term needs to be multiplied.

I was never good with variables and simple equations. Ah, I just want to go back to that time. :(