5xy+4x+7y+6x-3xy-4xy+3y
=5xy-3xy-4xy+4x+6x+7y+3y
=(5-3-4)xy+(4+6)x+(7+3)y
=-2xy+10x+10y
=-2xy+10(x+y)
因为x+y=3,xy=1
所以原式=-2xy+10(x+y)
=-2×1+10×3
=-2+30
=28
5xy+4x+7y+6x-3xy-4xy+3y
=5xy-3xy-4xy+4x+6x+7y+3y
=(5-3-4)xy+(4+6)x+(7+3)y
=-2xy+10x+10y
=-2xy+10(x+y)
因为x+y=3,xy=1
所以原式=-2xy+10(x+y)
=-2×1+10×3
=-2+30
=28