Cho A = 1/7 + 2/16 + 3/41 + 4/97 + 5/205. Chứng tỏ rằng A < 15/34

Question

Cho A = 1/7 + 2/16 + 3/41 + 4/97 + 5/205. Chứng tỏ rằng A < 15/34

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aikhanh 4 tháng 2021-08-16T17:35:51+00:00 1 Answers 7 views 0

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    2021-08-16T17:37:13+00:00

    Giải thích các bước giải:

     A<5/35+1/8+3/41+4/96+1/41

    =5/35+1/8+3/41+1/24+1/41

    =5/35+3/24+1/24+3/41+1/41

    =5/35+4/24+4/41

    =5/35+1/6+4/41

    =5/35+6/36+4/41

    Ta có: 5/35<5/34 ; 6/36<6/34 ; 4/41<4/34

    =>5/35+6/36+4/41<5/34+6/34+4/34=15/34

    Vậy: 1/7+2/16+3/41+4/7+5/205<15/34

     

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