4(x+2)=1-5y 3(y+2)=3-2x和x+y=420 30%x+40%y=160x80% 两个 求xy用加减消
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4(x+2)=1-5y 3(y+2)=3-2x和x+y=420 30%x+40%y=160x80% 两个 求xy用加减消元法,
![4(x+2)=1-5y 3(y+2)=3-2x和x+y=420 30%x+40%y=160x80% 两个 求xy用加减消](/uploads/image/z/9881864-8-4.jpg?t=4%28x%2B2%29%3D1-5y+3%28y%2B2%29%3D3-2x%E5%92%8Cx%2By%3D420+30%25x%2B40%25y%3D160x80%25+%E4%B8%A4%E4%B8%AA+%E6%B1%82xy%E7%94%A8%E5%8A%A0%E5%87%8F%E6%B6%88)
x=-3
y=1
xy=-3
30%x+40%y=160x80%
3x+4y=1280.1)
x+y=420.2)
1)-2)*3得:y=20
代人2):得:x=420-20=400
x=400,y=20
y=1
xy=-3
30%x+40%y=160x80%
3x+4y=1280.1)
x+y=420.2)
1)-2)*3得:y=20
代人2):得:x=420-20=400
x=400,y=20
4(x+2)=1-5y 3(y+2)=3-2x和x+y=420 30%x+40%y=160x80% 两个 求xy用加减消
x+y/2+x-y/3=6,4(x+y)-5(x-y)=2用加减消元法解方程组
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