已知x+y=4,xy=2,求代数式2(3x+2xy)+(2xy+3x+2y)-(4xy-7y)的值

问题描述:

已知x+y=4,xy=2,求代数式2(3x+2xy)+(2xy+3x+2y)-(4xy-7y)的值

原式=6x+4xy+2xy+3x+2y-4xy+7y
=9x+9y+2xy
=9(x+y)+2xy
=9×4+2×2
=36+4
=40