解方程组 x+y/5+x-y/2=7 4(x+y)-5(x-y)=2

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解方程组x+y/5+x-y/2=74(x+y)-5(x-y)=2解方程组x+y/5+x-y/2=74(x+y)-5(x-y)=2解方程组x+y/5+x-y/2=74(x+y)-5(x-y)=2方程1去

解方程组 x+y/5+x-y/2=7 4(x+y)-5(x-y)=2
解方程组 x+y/5+x-y/2=7 4(x+y)-5(x-y)=2

解方程组 x+y/5+x-y/2=7 4(x+y)-5(x-y)=2
方程1去分母得:
2(x+y)+5(x-y)=70 ③
方程2为:4(x+y)-5(x-y)=2 ④
3,4两式相加:6(x+y)=72,得x+y=12 ⑤
代入④得:48-5(x-y)=2,得x-y=46/5 ⑥
⑤+⑥:2x=106/5,得x=53/5
⑤-⑥:2y=14/5,得y=7/5