已知x+y=3,xy=1,求代数式(5x+2)-(3xy-5y)的值.
问题描述:
已知x+y=3,xy=1,求代数式(5x+2)-(3xy-5y)的值.
答
∵x+y=3,xy=1,
∴(5x+2)-(3xy-5y)
=5x+5y-3xy+2
=5(x+y)-3xy+2
=5×3-3+2
=14.