Decades: 60s BC 50s BC 40s BC 30s BC 20s BC - 10s BC - 0s 10s 20s 30s 40s
Years: 21 BC 20 BC 19 BC 18 BC 17 BC 16 BC 15 BC 14 BC 13 BC 12 BC 11 BC
Births
Deaths
... 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 ...