Respostas

2014-07-15T18:41:33-03:00
X²-2xy+y²-(x²+2xy+y²)= -20
x²-2xy+y²-x²-2xy-y²= -20
-4xy= -20
4xy=20
xy=20/4
xy=5

era so desenvolver a questao, bem simples.
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