(5x+2)-(3xy-5y)
=5x+2-3xy+5y
=5(x+y)-3xy+2
=5*3-3+2
=15-3+2
=14
去括号得5x+2-3xy+5y=5(x+y)-3xy+2由已知的5×3-3×1-2=13
原式=5X+5Y-1=15-1=14
(5x+2)-(3xy-5y)
=5x+2-3xy+5y=5(x+y)+2-3xy=15+2-3=14
(5x+2)-(3xy-5y)=5(x+y)-3xy+2
=5*3-3*1+2
=14