用二元一次方程解出来,20+60x+80y=70,20+80x+90y=80
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![用二元一次方程解出来,20+60x+80y=70,20+80x+90y=80](/uploads/image/z/2551232-56-2.jpg?t=%E7%94%A8%E4%BA%8C%E5%85%83%E4%B8%80%E6%AC%A1%E6%96%B9%E7%A8%8B%E8%A7%A3%E5%87%BA%E6%9D%A5%2C20%2B60x%2B80y%3D70%2C20%2B80x%2B90y%3D80)
用二元一次方程解出来,20+60x+80y=70,20+80x+90y=80
用二元一次方程解出来,20+60x+80y=70,20+80x+90y=80
用二元一次方程解出来,20+60x+80y=70,20+80x+90y=80
由①得:6x+8y=5 ③
由②得:8x+9y=6 ④
③X4得:24x+32y=20 ⑤
④X3得:24x+27y=18⑥
⑤-⑥得:5y=2
y=2/5
将y=2/5代入到③中得:6x+8*2/5=5
x=3/10
故x=3/10,y=2/5
(希望能帮到你.)