1/2.5+1/5.8+1/8.11+...+1/152.155
=1/3(3/2.5+3/5.8+3/8.11+...+3/152.155
=1/3(1/2-1/5+1/5-1/8+1/8-1/11+...+1/152-1/155)
=1/3(1/2-1/155)
=1/3(155/310-2/310)
=1/3.153/310=51/310
Kết quả:51/310
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