生石灰刷墙有毒吗:2(x+y)+3(x-y)=9(1) (x+y)+6(x-y)=9(2)
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快啊
①式乘2-②得,3(X+Y)=9,即X+Y=3
②乘2-①得,9(X-Y)=9,即X-Y=1
所以X=2,Y=1
5x - y = 9
7x-5y=9
x=2
y = 1
2(x+y)+3(x-y)=9(1) (x+y)+6(x-y)=9(2)
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