Decades: 1210s 1220s 1230s 1240s 1250s - 1260s - 1270s 1280s 1290s 1300s 1310s
Years: 1255 1256 1257 1258 1259 - 1260 - 1261 1262 1263 1264 1265
Births
Deaths
... our quadratic equation by a, we have <math> x^2 + \left( \frac{b}{a} \right) x + \frac{c}{a}=0 </math> which is ...