# Need help with inverse relations.

• Sep 15th 2009, 03:14 PM
lilmszbrina
Need help with inverse relations.
My teacher gave us this equation. y=2y^2 +x-3. The assignment was to find the inverse of the equation and determine whether it is a functiion or not.

I know it will be a function, but I'm not sure how to find the answer, which she gave to us. It is:

y= -1 [plus or minus] squareroot( 8x=25)
-------------------------------------
4

if you didnt understand that, in plain words it is y equals negative one plus or minus the square root of 8x plus 25. and then all that divided by 4. PLEASE HELP!
• Sep 15th 2009, 03:45 PM
pickslides
Quote:

Originally Posted by lilmszbrina
My teacher gave us this equation. y=2y^2 +x-3.

Are you sure the equation is \$\displaystyle y=2y^2 +x-3\$ . I would suggest it is probably \$\displaystyle y=2x^2 +x-3\$
• Sep 15th 2009, 03:48 PM
lilmszbrina
oh, typo i wasnt paying attention, but you are right.
• Sep 15th 2009, 04:05 PM
pickslides
In your PM you are now saying the equation is

\$\displaystyle y=x^2 +x-3\$

or is it?

\$\displaystyle y=2x^2 +x-3\$
• Sep 15th 2009, 04:07 PM
lilmszbrina
okay its the second one. im just being really careless sorry.
• Sep 15th 2009, 04:13 PM
pickslides
You need to swap x and y, then solve for y. To do this you need to complete the square.