Um... what's the difference?

  x = (-b ± √(b^2 - 4ac)) / 2a

Ok, remove a assuming it's 1 - well, yeah, less general math is simpler.

  x = (-b ± √(b^2 - 4c)) / 2

Move around 2 & 4... voila.

  x = -b/2 ± √(b^2 / 4 - c)

Like, whatever. :)