Decades: 1190s 1200s 1210s 1220s 1230s - 1240s - 1250s 1260s 1270s 1280s 1290s
Years: 1235 1236 1237 1238 1239 - 1240 - 1241 1242 1243 1244 1245
Births
Deaths
... solution(s) x to the quadratic equation <math>ax^2+bx+c=0</math> in terms of the coefficients a, b and c, which are assumed to be real (but see below for ...