8-2/3-2/15-2/35-2/63-2/99-2/143-2/195-2/255
=8-1+1/3-1/3+1/5-1/5+1/7-1/7+1/9-1/9+1/11-1/11+1/13-1/13+1/15-1/15+1/17
=7+1/17
=7又17分之1