Homework Help: solving quadratic equations by factoring

Posted by math1 on Sunday, December 19, 2010 at 7:35am.

the original dimensions of a rectangle were 15 by 20 cm. when both dimensons were decreased by the same amount, the area of the new rectangle is half the area of the original rectangle. find the dimensons of the new rectangle.

solving quadratic equations by factoring - Damon, Sunday, December 19, 2010 at 7:41am
(15-x)(20-x) = (1/2)(15*20)

2(15-x)(20-x) = 300

300 - 35 x + x^2 = 150

x^2 -35 x + 150 = 0

(x - 5)(x - 30) = 0
that is zero if
x = 5 or if x = 30

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