x+y=3,x-y=2
相加
2x=5
x=5/2
y=3-x=1/2
xy=5/4
原式=5x+2-3xy+5y
=5(x+y)-3xy+2
=5×3-3×5/4+2
=53/4
如x+y=3,x-y=2,那么(5x+2)-(3xy-5y)得值
如x+y=3,x-y=2,那么(5x+2)-(3xy-5y)得值
数学人气:733 ℃时间:2020-01-29 21:35:31
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