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.
(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