2020 . 2020 so sánh 2021.2019
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Ta có: \(2020^{45}-2020^{44}\)
\(=2020^{44}\cdot2020-2020^{44}\cdot1\)
\(=2020^{44}\cdot\left(2020-1\right)\)
\(=2020^{44}\cdot2019\)
Ta có: \(2020^{44}-2020^{43}\)
\(=2020^{43}\cdot2020-2020^{43}\cdot1\)
\(=2020^{43}\cdot\left(2020-1\right)\)
\(=2020^{43}\cdot2019\)
Vì \(2020^{44}>2020^{43}\)
nên \(2020^{44}\cdot2019>2020^{43}\cdot2019\)
hay \(2020^{45}-2020^{44}>2020^{44}-2020^{43}\)
Giải:
Ta có: N=2019+2020/2020+2021
=>N=2019/2020+2021 + 2020/2020+2021
Vì 2019/2020 > 2019/2020+2021 ; 2020/2021 > 2020/2020+2021
=>M>N
Vậy ...
Chúc bạn học tốt!
Ta có : \(\dfrac{2019}{2020}>\dfrac{2019}{2020+2021}\)
\(\dfrac{2020}{2021}>\dfrac{2020}{2020+2021}\)
\(\Rightarrow\dfrac{2019}{2020}+\dfrac{2020}{2021}>\dfrac{2019+2020}{2020+2021}\)
\(\Rightarrow M>N\)
Ta có: \(A=\left(2020^{2019}+2019^{2019}\right)^{2020}\)
\(=\left(2019^{2019}+2020^{2019}\right)^{2019}\cdot\left(2019^{2019}+2020^{2019}\right)\)
\(\Leftrightarrow\dfrac{A}{B}=\dfrac{\left(2019^{2019}+2020^{2019}\right)^{2019}\cdot\left(2019^{2019}+2020^{2019}\right)}{\left(2020^{2020}+2019^{2020}\right)^{2019}}\)
\(\Leftrightarrow\dfrac{A}{B}=\dfrac{2019^{2019}+2020^{2019}}{2019+2020}>1\)
\(\Leftrightarrow A>B\)
ta có
\(2021.2019=\left(2020+1\right)\left(2020-1\right)=2020.2020-1< 2020.2020\)
Vậy \(2021.2019< 2020.2020\)
2020.2020 và 2021.2019
2020.2019+2020 và 2020.2019+2019
Vậy 2020.2020>2021.2019