Decades: 1120s 1130s 1140s 1150s 1160s - 1170s - 1180s 1190s 1200s 1210s 1220s
Years: 1174 1175 1176 1177 1178 - 1179 - 1180 1181 1182 1183 1184
Births
Deaths
... "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, ...