怎么解二元一次方程组啊!求求大家了,课本中有道题是这样的:{2x-5y=7{2x+3y=-1 {2}-{1},得8y=-8y=-1将y=-1代入{1},得2x+5=7x=1.所以原方程解是{x=1{y=-1想问一下…这个为什么要{2}-{1}呢?还有8y=-8是怎么来
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![怎么解二元一次方程组啊!求求大家了,课本中有道题是这样的:{2x-5y=7{2x+3y=-1 {2}-{1},得8y=-8y=-1将y=-1代入{1},得2x+5=7x=1.所以原方程解是{x=1{y=-1想问一下…这个为什么要{2}-{1}呢?还有8y=-8是怎么来](/uploads/image/z/12551006-38-6.jpg?t=%E6%80%8E%E4%B9%88%E8%A7%A3%E4%BA%8C%E5%85%83%E4%B8%80%E6%AC%A1%E6%96%B9%E7%A8%8B%E7%BB%84%E5%95%8A%21%E6%B1%82%E6%B1%82%E5%A4%A7%E5%AE%B6%E4%BA%86%2C%E8%AF%BE%E6%9C%AC%E4%B8%AD%E6%9C%89%E9%81%93%E9%A2%98%E6%98%AF%E8%BF%99%E6%A0%B7%E7%9A%84%EF%BC%9A%7B2x-5y%3D7%7B2x%2B3y%3D-1+%7B2%7D-%7B1%7D%2C%E5%BE%978y%3D-8y%3D-1%E5%B0%86y%3D-1%E4%BB%A3%E5%85%A5%7B1%7D%2C%E5%BE%972x%2B5%3D7x%3D1.%E6%89%80%E4%BB%A5%E5%8E%9F%E6%96%B9%E7%A8%8B%E8%A7%A3%E6%98%AF%7Bx%3D1%7By%3D-1%E6%83%B3%E9%97%AE%E4%B8%80%E4%B8%8B%E2%80%A6%E8%BF%99%E4%B8%AA%E4%B8%BA%E4%BB%80%E4%B9%88%E8%A6%81%7B2%7D-%7B1%7D%E5%91%A2%3F%E8%BF%98%E6%9C%898y%3D-8%E6%98%AF%E6%80%8E%E4%B9%88%E6%9D%A5)
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