己知x+y=-4,xy=3,求4(xy+2y)+[6x+(2xy-5y-3x)]的值

问题描述:

己知x+y=-4,xy=3,求4(xy+2y)+[6x+(2xy-5y-3x)]的值

原式=4xy+8y+6x+2xy-5y-3x
=6xy+3x+3y
=6*3+3(x+y)
=18-12=6