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)

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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!