giúp nha so sánh A = $\frac{2019}{2020}$ + $\frac{2020}{2021}$ và B = $\frac{2019+2020}{2020+2021}$

0 bình luận về “giúp nha so sánh A = $\frac{2019}{2020}$ + $\frac{2020}{2021}$ và B = $\frac{2019+2020}{2020+2021}$”

1. Đáp án:

    Ta có:2019+2020/2020+2021=2019/2020+2021 +2020/2020+2021

   Vì 2019/2020+2021<2019/2020

      2020/2020+2021<2020/2021

   =>2019/2020+2020/2021>2019/2020+2021+2020/2020+2020=2019+2020/2020+2021

   HAY A>B

    

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2. Đáp án:Giải thích các bước giải:

   $\color{red}{Lemon .}$

   Xét :  $A=\dfrac{2019}{2020}+$ $\dfrac{2020}{2021}.$ 

   Ta có : $\dfrac{2019}{2020}>$ $\dfrac{2019}{2020+2021}$ 

              $\dfrac{2020}{2021}>$ $\dfrac{2020}{2020+2021}$

   $⇒A=\dfrac{2019}{2020}+$$\dfrac{2020}{2021}>$$\dfrac{2019}{2020+2021}$$\dfrac{2020}{2020+2021}=$$\dfrac{2019+2020}{2020+2021}=B$

   vậy A > B . 

    

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