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加减消元法解二元一次方程组,要标准过程.

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加减消元法解二元一次方程组,要标准过程.
(1){x+y/2+x-y/2=7 4(x+y)-5(x-y)=2
(2){x+y=360 112%x+110%y=400
(1)x+y/2+x-y/2=7 ················1
4(x+y)-5(x-y)=2··················2
1式X10+2式得:
9(x+y)=72 即:x+y=8 ·············3
1式X8-2式得:
9(x-y)=54 即:x-y=6···············4
由3式-4式得:
2y=2 解得:y=1
由3式+4式得:
2x=14 解得:x=7
(2){x+y=360 ···························1
112%x+110%y=400······················2
由1式X110%-2式得:
1.1x-1.12x=396-400
-0.02x=-4
解得:x=200 代入1式得:
y=160