SOLUTION: Greetings mathematic overlords, My conundrum is as follows, I have this equation I am using to calculate a few values: 2x-(x/10)^2=y, from 0 to 100 Now this equation isn

Question 608098: Greetings mathematic overlords,
My conundrum is as follows, I have this equation I am using to calculate a few values:
2x-(x/10)^2=y, from 0 to 100
Now this equation isn�t especially difficult and I get plenty of values out of it, such as when x=36 y=59.04, when x=20 y=26, when x=100 y=100, plotting a nice curve.
My issue now is that I need a way to somehow reverse this formula, so that when I know �y� but not �x� I can find �x�. I�ve spent a good hour now trying to come up with any tangible way to calculate �x� by only knowing �y� but it is simply beyond my abilities.
If it�s not too much trouble would you be able to help me find the formula to find �x� from only �y� so that all answers tie in with the equation 2x-(x/10)^2=y?
If possible it would be a great help to me if you were able to explain just how to come to determine such a formula so that I can work it out for myself in the future for similar equations.
Thank you for your time.

Answer by scott8148(6628) (Show Source): You can put this solution on YOUR website!
2x - x^2 / 100 = y

200x - x^2 = 100y ___ x^2 - 200x = -100y

completing the square ___ x^2 - 200x + 10000 = 10000 - 100y

(x - 100)^2 = 100(100-y)

taking square root ___ x - 100 = � 10 √(100-y) ___ x = 100 � 10 √(100-y)

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