解方程组:{3(x+y)-2(x-y)=9,5(x+y)+2(x-y)=-1}
问题描述:
解方程组:{3(x+y)-2(x-y)=9,5(x+y)+2(x-y)=-1}
答
3﹙x+y﹚-2﹙x-y﹚=9………………①
5﹙x+y﹚+2﹙x-y﹚=﹣1……………②
①+②得:x+y=1……………………③
②代入②得:x-y=﹣3………………④
③+④得:x=﹣1
③-④得:y=2