Echidna ("she viper") was a female monster in Greek mythology, usually considered offspring of Uranus and Gaia, or sometimes Ceto. She had the face of a beautiful woman but the body of a serpent. When she and her mate, Typhon, attacked the Olympians, Zeus beat them back but allowed Typhon, Echidna and their children to live as a challenge to future heroes.
... from both sides, we get
<math>x=\frac{-b}{2a}\pm\frac{\sqrt{b^2-4ac}}{2a}=\frac{-b\pm\sqrt{b^2-4ac}}{2a}.</math>
Generalizations
The formula and ...