TA có: \(T=\frac{-2\left|x-2018\right|-2021}{\left|x-2018\right|+2020}\)
\(=\frac{-2\left|x-2018\right|-4040+2019}{\left|x-2018\right|+2020}=-2+\frac{2019}{\left|x-2018\right|+2020}\)
Ta có: \(\left|x-2018\right|+2020\ge2020\forall x\)
=>\(\frac{2019}{\left|x-2018\right|+2020}\le\frac{2019}{2020}\forall x\)
=>\(\frac{2019}{\left|x-2018\right|+2020}-1\le\frac{2019}{2020}-2=-\frac{2021}{2020}\forall x\)
Dấu '=' xảy ra khi x-2018=0
=>x=2018
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