x+y=70 2x-4y=80怎么解,
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x+y=70 2x-4y=80怎么解,
x+y=70 2x-4y=80怎么解,
x+y=70 2x-4y=80怎么解,
x+y=70
x=70-y
带入 2x-4y=80
2*( 70-y)-4y=80
140-2y-4y=80
6y=60
y=10
x=70-10=60
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x+y=70 2x-4y=80怎么解,
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