先化简再求值(2x-3y+5xy)-(x-4y-3xy),其中x+y=-3,xy=-4
问题描述:
先化简再求值(2x-3y+5xy)-(x-4y-3xy),其中x+y=-3,xy=-4
答
(2x-3y+5xy)-(x-4y-3xy)
=2x-3y+5xy-x+4y+3xy
=2x-x-3y+4y+5xy+3xy
=x+y+8xy
=(x+y)+8(xy)
=-3+8*(-4)
=-3-32
=-35