Decades: 1160s 1170s 1180s 1190s 1200s - 1210s - 1220s 1230s 1240s 1250s 1260s
Years: 1207 1208 1209 1210 1211 - 1212 - 1213 1214 1215 1216 1217
Births
Deaths
... Since "2xy" in this case is (b/a)x, we must have y = b/(2a), so we add the square of b/(2a) to both sides, ...