a、b互为相反数,a+b=0
c、d互为倒数,cd=1
|x|=2,y=1,x（a+b+1）x*2+cdy*2+x*2y-xy*2
=(0+1)(-2)*2+1X1*2+(-2)*2X1-(-2)X1*2
=4+2+4+2
=12