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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 7: Chứng tỏ rằng : n/n+1 < n+1/n+2 ∀n ∈N

Toán Lớp 7: Chứng tỏ rằng : n/n+1 < n+1/n+2 ∀n ∈N

Comments ( 2 )

  1. \text {Mon}
    Ta có: 1 – $\dfrac{n}{n+1}$ = $\dfrac{1}{n+1}$ 
              1 – $\dfrac{n+1}{n+2}$ = $\dfrac{1}{n+2}$ 
    Vì n + 1 < n + 2 nên $\dfrac{1}{n+1}$  > $\dfrac{1}{n+2}$ 
    ⇒$\dfrac{n}{n+1}$<$\dfrac{n+1}{n+2}$
    Vậy $\dfrac{n}{n+1}$<$\dfrac{n+1}{n+2}$
     

  2. Có:
    Để có giá trị bằng 1
    n/(n + 1) + 1/(n + 1)
    (n + 1)/(n + 2) + 1/(n + 2)
    Vì:
    1/(n + 1) > 1/(n + 2) (n + 1 < n + 2)
    ⇒ n/(n + 1) < (n + 1)/(n + 2)
     

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222-9+11+12:2*14+14 = ? ( )

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