Originally from the CIA World Factbook 2000, with bits added from the U.s. Department of State site.
... to both sides, getting <math>x^2+\frac{b}{a}x+\frac{b^2}{4a^2}=-\frac{c}{a}+\frac{b^2}{4a^2}.</math> The left side is now a perfect square; it is the ...