CỨU MÌNH VỚI, MÌNH CẦN GẤP

Đáp án: D

Giải thích các bước giải:

$\begin{array}{l}
A = \dfrac{{\left| {x - 2021} \right| - 2022}}{{\left| {x - 2021} \right| + 2022}}\\
 = \dfrac{{\left| {x - 2021} \right| + 2022 - 4044}}{{\left| {x - 2021} \right| + 2022}}\\
 = 1 - \dfrac{{4044}}{{\left| {x - 2021} \right| + 2022}}\\
Do:\left| {x - 2021} \right| \ge 0\\
 \Leftrightarrow \left| {x - 2021} \right| + 2022 \ge 2022\\
 \Leftrightarrow \dfrac{1}{{\left| {x - 2021} \right| + 2022}} \le \dfrac{1}{{2022}}\\
 \Leftrightarrow \dfrac{{4044}}{{\left| {x - 2021} \right| + 2022}} \le \dfrac{{4044}}{{2022}} = 2\\
 \Leftrightarrow  - \dfrac{{4044}}{{\left| {x - 2021} \right| + 2022}} \ge  - 2\\
 \Leftrightarrow 1 - \dfrac{{4044}}{{\left| {x - 2021} \right| + 2022}} \ge 1 - 2\\
 \Leftrightarrow A \ge  - 1\\
 \Leftrightarrow GTNN:A =  - 1\,khi:x = 2021
\end{array}$