Stuff

ax^2 + bx + c = 0
x^2 + bx/a + c/a = 0
(x + b/2a)^2 -(b/2a)^2 + c/a = 0
(x + b/2a)^2 = (b/2a)^2 - c/a
x + b/2a = +/- sqrt( (b/2a)^2 - c/a )
x = -b/2a +/- sqrt( (b/2a)^2 - c/a )
x = -b/2a +/- sqrt( b^2/4a^2 - c/a )
x = -b/2a +/- sqrt( (ab^2 - 4ca^2)/4a^3 )
x = -b/2a +/- sqrt( (b^2 - 4ca)/4a^2 )
x = -b/2a +/- sqrt( b^2 - 4ca )/2a   :  note that +/- divided by +/- still only gives two cases : +/-  :)
x = ( -b +/- sqrt( b^2 - 4ca ) )/2a