a,b互为相反数,c,d互为倒数,x的绝对值等于1,
=>a+b=0,cd=1,|x|=1 =>x=1或-1
x=1时
a+b-x+cd/x
=0-1+1
=0
x=-1时
a+b-x+cd/x
=0-(-1)+(-1)
=1-1
=0