计算:1/2加1/6加1/12加1/20加1/30加1/42加1/56的简便方法
问题描述：
计算:1/2加1/6加1/12加1/20加1/30加1/42加1/56的简便方法
答
=1/1*2+1/2*3+1/3*4+1/4*5+1/5*6+1/6*7+1/7*8
=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