3/2-5/6+7/12-9/20-11/30-13/42
=9/6-5/6+7/12-9/20-11/30-13/42
=2/3+7/12-9/20-11/30-13/42
=8/12+7/12-9/20-11/30-13/42
=5/4-9/20-11/30-13/42
=25/20-9/20-11/30-13/42
=4/5+11/30-13/42
=24/30+11/30-13/42
=35/30-13/42
=(245/210-65/210)
=180/210
=6/7
=(1+1/2)-(1/2+1/3)+(1/3+1/4)-(1/4+1/5)+(1/5+1/6)-(1/6+1/7)
=1+1/2-1/2-1/3+1/3+1/4-1/4-1/5+1/5+1/6-1/6-1/7
=1-1/7
=6/7
内容全部来源于网络收集，如有侵权，请联系网站删除：QQ：24596024