Centuries: 12th century - 13th century - 14th century
Decades: 1210s 1220s 1230s 1240s 1250s - 1260s - 1270s 1280s 1290s 1300s 1310s
Years: 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269
... quadratic equation by a, we have <math> x^2 + \left( \frac{b}{a} \right) x + \frac{c}{a}=0 </math> which is equivalen ...