两方程相加,得:
7x+7y=35===>>>>x+y=5
两方程相减,得:
y-x=21===>>>x-y=-21
已知二元一次方程3x+4y=28,4x+3y=7,不解方程组,则x+y= ,x-y= .
已知二元一次方程3x+4y=28,4x+3y=7,不解方程组,则x+y= ,x-y= .
数学人气:713 ℃时间:2019-11-01 11:52:26
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