1/8+1/15+1/24+...+1/143
=1/2X4+1/3X5+1/4X6+...1/11X13
=1/2(1/2-1/4+1/3-1/5+1/4-1/6+...+1/11-1/13)
注意到前后各剩两项得
=1/2(1/2+1/3-1/12-1/13)
1/8+1/15+1/24+...+1/143
=1/2X4+1/3X5+1/4X6+...1/11X13
=1/2(1/2-1/4+1/3-1/5+1/4-1/6+...+1/11-1/13)
注意到前后各剩两项得
=1/2(1/2+1/3-1/12-1/13)