2/8+2/28+2/77+2/176+2/352
原式=1/4+1/14+(1/2)(1/7-1/11)+(1/3)(1/8-1/11)+(1/5)(1/11-1/16)=1/4+1/14+1/2*1/7-1/2*1/11+1/3*1/8-1/3*1/11+1/5*1/11-1/80=(1/4+1/24-1/80)+(1/14+1/14)-(1/2+1/3-1/5)*1/11=7/24-1/80+1/7-19/30*1/11=67/240-19/330+1/7=39/176+1/7=449/1232