Decades: 1210s 1220s 1230s 1240s 1250s - 1260s - 1270s 1280s 1290s 1300s 1310s
Years: 1261 1262 1263 1264 1265 - 1266 - 1267 1268 1269 1270 1271
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... roots numerically, the usual form of the quadratic formula is not ideal. See Loss of significance for details. Derivation The quadratic formula is derived by ...