先化简,再求值.[(x+2y)-(x+2y)(3x-y)-5y]÷2y,其中x=-2,3Q
问题描述：
先化简,再求值.[(x+2y)-(x+2y)(3x-y)-5y]÷2y,其中x=-2,3Q
答
[(x+2y)-(x+2y)(3x-y)-5y]÷2y 解原式=[x+4xy+4y-3x+5x-7y-5y]÷2y =[4xy+4y-2x+5x-12y]÷2y 当x=-2 y=1/2时 =-4+1-8-10-5 =-3-8-10-5 =-11-10-5 =-26