a与b互为相反数,c与d互为倒数,x=4(a+2)-(a-3b),y=c²d+d²-(d／c+c-1

a与b互为相反数所以：a+b=0c与d互为倒数所以：cd=1x=4(a+2)-(a-3b),=3(a+b)+8=8y=c²d+d²-(d／c+c-1),=c+d²-(d／c+c-1)通分=(c^2+cd^2-d-c^2+c)/c=1将x=8,y=1带入xy／4-(3x-5y)／8式子中得出：-3/8