a+b/m-n+x²-cdxcd互为倒数,ab互为相反数则a+b/m-n+x²-cdx=a-a/m-n+x²-x=a-a/m-n+4-x当x=2时,a+b/m-n+x²-cdx=a-a/m-n+2当x=-2时,a+b/m-n+x²-cdx=a-a/m-n+6