(1/2+1/3+1/4+1/5)*(1/3+1/4+1/5+1/6)-(1/2+1/3+1/4+1/5+1/6)*(1/3+1/4+1/5)
參考答案:(1/2+1/3+1/4+1/5)*(1/3+1/4+1/5+1/6)-(1/2+1/3+1/4+1/5+1/6)*(1/3+1/4+1/5)=(1/2+1/3+1/4+1/5)*(1/3+1/4+1/5)+(1/2+1/3+1/4+1/5)*1/6-(1/2+1/3+1/4+1/5)*(1/3+1/4+1/5)-1/6*(1/3+1/4+1/5)=(1/2+1/3+1/4+1/5)*1/6-1/6*(1/3+1/4+1/5)=1/2*1/6+(1/3+1/4+1/5)*1/6-1/6*(1/3+1/4+1/5)=1/2*1/6=1/12