Centuries: 2nd century - 3rd century - 4th century
Decades: 170s 180s 190s 200s 210s - 220s - 230s 240s 250s 260s 270s
Years: 220 221 222 223 224 - 225 - 226 227 228 229 230
Births
Deaths
... These solutions are also called the roots of the equation. The formula reads <math> x=\frac{-b \pm \sqrt {b^2-4ac}}{2a} </math> The term b2 – 4ac ...