Decades: 1180s 1190s 1200s 1210s 1220s - 1230s - 1240s 1250s 1260s 1270s 1280s
Years: 1226 1227 1228 1229 1230 - 1231 - 1232 1233 1234 1235 1236
Deaths
Events
... the usual form of the quadratic formula is not ideal. See Loss of significance for details. Derivation The quadratic formula is derived by the method of completing ...