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a: 21^15=3^15*7^15

27^5*49^8=3^15*7^14

mà 15>14

nên 21^15>27^5*49^8

b: \(2020^{2020}-2020^{2019}=2020^{2019}\left(2020-1\right)=2020^{2019}\cdot2019\)

\(2020^{2019}-2020^{2018}=2020^{2018}\cdot2019\)

mà 2019>2018

nên 2020^2020-2020^2019>2020^2019-2020^2018

26 tháng 7 2023

cảm ơn ạ

Ta có: \(A=\left(2020^{2019}+2019^{2019}\right)^{2020}\)

\(=\left(2019^{2019}+2020^{2019}\right)^{2019}\cdot\left(2019^{2019}+2020^{2019}\right)\)

\(\Leftrightarrow\dfrac{A}{B}=\dfrac{\left(2019^{2019}+2020^{2019}\right)^{2019}\cdot\left(2019^{2019}+2020^{2019}\right)}{\left(2020^{2020}+2019^{2020}\right)^{2019}}\)

\(\Leftrightarrow\dfrac{A}{B}=\dfrac{2019^{2019}+2020^{2019}}{2019+2020}>1\)

\(\Leftrightarrow A>B\)

12 tháng 3 2022

undefined

12 tháng 3 2022

\(a.=\dfrac{2019}{2020}\times\left(\dfrac{4}{11}+\dfrac{5}{11}+\dfrac{2}{11}\right)\\ =\dfrac{2019}{2020}\times1=\dfrac{2019}{2020}\\ b.=\dfrac{25}{27}\times\left(\dfrac{17}{14}-\dfrac{1}{14}-\dfrac{2}{14}\right)\\ =\dfrac{25}{27}\times1=\dfrac{25}{27}\)

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 : \(\dfrac{2019}{2020}>\dfrac{2019}{2020+2021}\)

            \(\dfrac{2020}{2021}>\dfrac{2020}{2020+2021}\)

\(\Rightarrow\dfrac{2019}{2020}+\dfrac{2020}{2021}>\dfrac{2019+2020}{2020+2021}\)

\(\Rightarrow M>N\)

Tham khảo:

loading...

2 tháng 1 2020

\(x=\frac{2019^{2020}+1}{2019^{2019}+1}>\frac{2019^{2020}+1+2018}{2019^{2019}+1+2018}=\frac{2019^{2020}+2019}{2019^{2019}+2019}=\frac{2019\left(2019^{2019}+1\right)}{2019\left(2019^{2018}+1\right)}=\frac{2019^{2019}+1}{2019^{2018}+1}\)(1)

\(y=\frac{2019^{2019}+2020}{2019^{2018}+2020}< \frac{2019^{2019}+2020-2019}{2019^{2018}+2020-2019}=\frac{2019^{2019}+1}{2019^{2018}+1}\left(2\right)\)

Từ (1) và (2) \(\Rightarrow x>y\)

11 tháng 3 2020

Bạn hãy dựa vào link này mà tự làm nhé : 

https://olm.vn/hoi-dap/detail/246211413079.html

Bài làm của mình đó !