1/2+1/6+1/12+1/20+1/30+1/42+1/56怎么做?我已经知道算式了,但我想求答案.1/1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8=（一个算式）=得数.

1/2+1/6+1/12+1/20+1/30+1/42+1/56怎么做?我已经知道算式了,但我想求答案.1/1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8=（一个算式）=得数.
1/2+1/6+1/12+1/20+1/30+1/42+1/56怎么做?
我已经知道算式了,但我想求答案.1/1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8=（一个算式）=得数.

1/2+1/6+1/12+1/20+1/30+1/42+1/56怎么做?我已经知道算式了,但我想求答案.1/1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8=（一个算式）=得数.
1/1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8
=1-1/8
=7/8