(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)
=-2xy+2x+3y-3xy-2y+2x-x-4y-xy
=-6xy+3x-3y
=-6xy+3*(x-y)
当时,原式=-6*1+3*4=6
所以(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)的值为6