5/1.3+5/3.5+5/5.7+…+5/99.101 Tính tổng

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1. `5/1.3+5/3.5+5/5.7+…+5/99.101`
   ` = 5/2.(2/1.3 + 2/3.5 + 2/5.7 + .. + 2/99.101)`
   ` = 5/2 . (1-1/3 + 1/3 – 1/5 + 1/5 -1/7 + …+ 1/99-1/101)`
   ` = 5/2 . (1-1/101)`
   ` = 5/2 . 100/101`
   ` = 250/101`

    

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2. 5/1.3+5/3.5+5/5.7+…+5/99.101

   =2/1.3.5/2+2/3.5.5/2+2/5.7.5/2+…….+2/99.101.5/2

   =5/2.(2/1.3+2/3.5+2/5.7+…..+2/5.7)

   =5/2.100/101

   =250/101.

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