MATHS.. about Quadratic Equations in One Unknown (2)

1) The dimensions of a rectangular picture are 16cmx 20cm. The picture is surrounded with a wooden frame of unifoem with. Of the are of the fram is 252cm², find its width.
Let the width be x cm,
(16 + 2x)(20 + 2x) - (16) ( 20) = 252
(8 + x)(10 + x) - 80 = 63
80 + 18x + x^2 - 80 = 63
x^2 + 18x - 63 = 0
(x + 21)(x - 3) = 0
x = -21(rejected) or x = 3


Answer: 1) 3 cm