math
posted by amanda .
the printed matter on a 18 by 22 centimeter page of a book must cover 96 square centimeters.If all margins are to be the same width, how wide should they be?

Let x = margin width.
(18  2x)(22  2x) = 96
396  80x +4x^2 = 96
300 80x +4x^2 = 0
x^2 20x + 75 = 0
(x15)(x5) = 0
x = 5 cm is the only margin width that results in positive length and width of the printed area.