Centuries: 5th century - 6th century - 7th century
Decades: 500s 510s 520s 530s 540s - 550s - 560s 570s 580s 590s 600s
Years: 550 551 552 553 554 555 556 557 558 559 560
Events
Births
Deaths
... in this case is (b/a)x, we must have y = b/(2a), so we add the square of b/(2a) to both sides, ...