2007x-2008y=2009,x+y=1,求4017x-4013y+4018的值?
1.如果2007x-2008y=2009,x+y=1,不解方程组求4017x-4013y+4018的值.2.若x-2y=
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当x-y/x+y=2009/2010时,求代数式2009(x+y)/x-y+4020(x-y)/x+y的值.
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