二分之一加上六分之一+十二分之一+二十分之一三十分之一+四十二分之一利用规律怎么算
问题描述：
二分之一加上六分之一+十二分之一+二十分之一三十分之一+四十二分之一利用规律怎么算
答
1/2+1/6+1/12+1/20+1/30+1/42
=1/1*2+1/2*3+1/3*4+1/4*5+1/5*6+1/6*7
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7
=1-1/7
=6/7
IT'S easy!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
答
1/2+1/6+1/12+1/20+1/30+1/42
=1/1*2+1/2*3+1/3*4+1/4*5+1/5*6+1/6*7
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7
=1-1/7
=6/7