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642

Centuries: 6th century - 7th century - 8th century

Decades: 590s 600s 610s 620s 630s - 640s - 650s 660s 670s 680s 690s

Years: 637 638 639 640 641 - 642 - 643 644 645 646 647


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Quadratic formula

... this means that the parabola described by the quadratic equation touches the x-axis in a single point.) If the discriminant is positive, then there are two differen ...

 
 
 
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