(1-1/2)+(1/2-1/3)+(1/3-1/4)......+(1/1999-1/2000)
1-1/2+1/2-1/3+1/3-1/4+……+1/1998-1/1999+1/1999-1/2000
=1-(1/2-1/2)-(1/3-1/3)-.......(1/1999-1/1999)-1/2000
=1-1/2000
=1999/2000
我是老师 谢谢采纳
1-1/2+1/2-1/3+1/3-1/4……+1/1999-1/2000
=1-1/2000
=1999/2000
去掉括号
=1-1/2+1/2-1/3+1/3.......-1/1999+1/1999-1/2000
=1-1/2000
=1999/2000
(1-1/2)+(1/2-1/3)+(1/3-1/4)+……(1/1999-1/2000)
=1-1/2+1/2-1/3+1/3-1/4+……+1/1998-1/1999+1/1999-1/2000
=1-1/2000
=1999/2000
1-1/2000=1999/2000