就1道数学题,帮个忙啦已知X^2+Y^2=7,XY=2,求5X^2 -3XY -4Y^2 -11XY -7X^2 +2Y
2个回答
5X^2 -3XY -4Y^2 -11XY -7X^2 +2Y^2
=-2x^2-14xy-2y^2
=-2(x^2+y^2)-14xy
=-2*7-14*2
=-42
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