1/8+1/24+1/48+1/80+1/120
=1/(2×4)+1/(4×6)+1/(6×8)+1/(8×10)+1/(10×12)
=1/2×(1/2-1/4)+1/2×(1/4-1/6)+1/2×(1/6-1/8)+1/2×(1/8-1/10)+1/2×(1/10-1/12)
=1/2×(1/2-1/4+1/4-1/6+1/6-1/8+1/8-1/10+1/10-1/12)
=1/2×(1/2-1/12)
=1/2×5/12
=5/24
明白请采纳，有疑问请追问！
有新问题请求助，谢谢!
11/8+1/24+1/48+1/80+1/120
=33/24+1/24+1/48+(1/80+1/120)
=34/24+1/48+5/240
=69/48+1/48
=70/48
=35/24
11/8+1/2×（1/4-1/6+1/6-1/8+1/8-1/10+1/10-1/12）
=11/8+1/2×（1/4-1/12）
=11/8+1/12
=35/24
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