Decades: 1230s 1240s 1250s 1260s 1270s - 1280s - 1290s 1300s 1310s 1320s 1330s
Years: 1277 1278 1279 1280 1281 - 1282 - 1283 1284 1285 1286s[?] 1287
Births
Deaths
... (but see below for generalizations) with a being non-zero. These solutions are also called the roots of the equation. The formula reads <math> x=\frac{-b \pm ...