How do i make a parabola change direction without rewriting function

^Topic.

I'm working on a system (this is NOT homework, so full help is appreciated).

I am looking to display text with this: A^2 - A = Y and A = X (Those will map the 2D XY point for the location of the text. The problem is, that parabola will execute from bottom left to top right independent of the position of the being.

I.E

A = 1 so X = 1, Y = 0

A = 2 so X = 2, Y = 2

A = 3 so X = 3, Y = 6

A = 4 so X = 4, Y = 12

And it will keep going like that.

The problem is, I want it to change direction based on the relation of the two beings' XY.

I know i probably messed up on the explanation (a LOT =p), so if you need me to explain it better just ask.

Thanks!