Centuries: 6th century - 7th century - 8th century
Decades: 590s 600s 610s 620s 630s - 640s - 650s 660s 670s 680s 690s
Years: 642 643 644 645 646 - 647 - 648 649 650 651 652
Births
Deaths
... formula The quadratic formula expresses the explicit solution(s) x to the quadratic equation <math>ax^2+bx+c=0</math> in terms of th ...