1. ## Isolating a Variable

Can anyone isolate a from this equation:

(x-a)^2 = x^2 + y^2

thanks.

I get as far as a = y^2/a-2x, but don't know where to go fro there.

2. I can

$(x-a)^2 = x^2 + y^2$

$x-a = \sqrt{x^2 + y^2}$

$-a = \sqrt{x^2 + y^2}-x$

$a =x- \sqrt{x^2 + y^2}$

3. Thanks, it was suprisingly simple, I was just starting from the wrong place. Thanks again!

EDIT: I've stumpled upon another algebretic type problem,
using the above value for a is it possible to prove that
(y/-a)^2 = -1?

I'm stumped.