\(\dfrac{1}{x}+\dfrac{1}{y}+\dfrac{1}{z}=\dfrac{1}{2022}\)

\(\Rightarrow\dfrac{yz+zx+xy}{xyz}=\dfrac{1}{x+y+z}\)

\(\Rightarrow\left(yz+zx+xy\right)\left(x+y+z\right)=xyz\)

\(\Rightarrow xy\left(x+y\right)+yz\left(y+z\right)+zx\left(z+x\right)+3xyz-xyz=0\)

\(\Rightarrow xy\left(x+y\right)+yz\left(y+z\right)+zx\left(z+x\right)+2xyz=0\)

\(\Rightarrow\left(x+y\right)\left(y+z\right)\left(z+x\right)=0\)

\(\Rightarrow x=-y\) hoặc \(y=-z\) hoặc \(z=-x\).

-Đến đây thôi bạn, câu hỏi sai rồi ạ.

\(P=\dfrac{1}{2021}\left(\dfrac{2021^2}{x}+\dfrac{1}{y}\right)\ge\dfrac{1}{2021}.\dfrac{\left(2021+1\right)^2}{x+y}=\dfrac{1}{2021}.\dfrac{2022^2}{\dfrac{2022}{2021}}=2022\)

\(P_{min}=2022\) khi \(\left(x;y\right)=\left(1;\dfrac{1}{2021}\right)\)

Cứu với ;-;

1: \(M=0\)

mà \(\left\{{}\begin{matrix}\left(x-2021\right)^{2022}>=0\\\left(2021-y\right)^{2020}>=0\end{matrix}\right.\)

nên x-2021=0 và 2021-y=0

=>x=2021 và y=2021

<=> x-2021=0 và y+2022=0

=>x=2021 và y=-2022

Vì \(\left(x-2021\right)^2\ge0,\left(y+2022\right)^2\ge0\)

\(\Rightarrow\left(x-2021\right)^2+\left(y+2022\right)^2\ge0\)

Dấu "=" xảy ra \(\Leftrightarrow\left\{{}\begin{matrix}x-2021=0\\y+2022=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=2021\\y=-2022\end{matrix}\right.\)

Vậy \(\left(x,y\right)=\left(2021,-2022\right)\)