解答:
1/2+1/6+1/12+1/20+1/30
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6
=1-1/6
=5/6
1-1/2+1/2-1+1/3-1/4+1/20+1/30
=1/2+1/2-1+1/12+1/20+1/30
=1/12+1/20+1/30
=1/6
好辛苦....~~~~
1-1\2+1\2-1\3...+1\5-1\6
1-1\6
5\6
已知:1-1/2=1/2,1/2-1/3=1/6,1/3-1/4=1/12,求1/2+1/6+1/12+1/20+1/30.
2