可以裂项再相加
kde235
2024-07-16 06:12:36
( reads)
3/10+3/40+3/88+3/154+3/238+3/340
= (1/2 - 1/5) + (1/5 - 1/8) + (1/8 - 1/11) + (1/11 - 1/14) + (1/14 - 1/17) + (1/17 - 1/20)
= 1/2 - 1/20
= 9/20
yma16
2024-07-16 11:26:08高。看看这个：1x2+2x3+...+19x20