∵a+x2=2007，b+x2=2008，c+x2=2009，∴b-a=1，c-b=1，c-a=2，∴abc+bac+cab−1a−1b−1c=abc−1b+bac−1c+cab−1a=a−cbc+b−aac+c−bab=−2bc+1ac+1ab=−2a+b+cabc=(b−a)+(c−a)abc=1+224=18．...