Respostas

2013-10-18T17:56:29-03:00
 \left \{ {{2x + 2y =20}\atop {x. y = 21}} \right.
(2x + 2y = 20 : 2 --> x + y = 10 ----> x = 10 - y)
x . y = 21
(10 - y).y = 21
10y - y^2 = 21
- y^2 + 10y - 21 = 0 .(-1)         
 y^2 - 10y + 21 = 0
delta = 16
x' = 7
x"= 3
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Perímetro = 2.7 + 2.3 = 14 + 6 = 20
Área = 7 . 3 = 21
17 4 17