{5x+7y=530 {2x+4y=260
解方程组(x+y)(x-2y)=-5 (x-y)(x+2y)=7
3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27
已知x*x+4x+y*y-2y+5=0,则x*x+y*y=?
方程2分之x+y+2分之x-y=7,4(x+y)-5(x-y)=2
{5x+7y=530 {2x+4y=260
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