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
... We get <math>\left(x+\frac{b}{2a}\right)^2=\frac{-4ac+b^2}{4a^2}=\frac{b^2-4ac}{4a^2}.</math> Taking square roots of bo ...