a, \(\left|x\right|=7\Leftrightarrow\left[{}\begin{matrix}x=7\\x=-7\end{matrix}\right.\) \(\left(tm\right)\)
Vậy \(x\in\left\{7;-7\right\}\) là giá trị cần tìm
b, \(\left|x\right|< 7\)
Mà \(\left|x\right|\ge0\)
\(\Leftrightarrow\left|x\right|\in\left\{0;1;2;3;4;5;6\right\}\)
\(\Leftrightarrow x\in\left\{0;-1;1;-2;2;-3;3;-4;4;-5;5;-6;6\right\}\)
b, tương tự
a) \(\left|x\right|=7\Leftrightarrow\left[{}\begin{matrix}x=7\\x=-7\end{matrix}\right.\)
Vậy ....
b) \(\left|x\right|< 7\Leftrightarrow-7< x< 7\Leftrightarrow x\in\left\{-6;-5;...;5;6\right\}\)
Vậy .....
c) \(\left|x\right|>7\Leftrightarrow\left[{}\begin{matrix}x>7\\x< -7\end{matrix}\right.\)
Vậy....
\(\left|x\right|=7\) \(\Rightarrow\left[{}\begin{matrix}x=7\\x=-7\end{matrix}\right.\)
\(\left|x\right|< 7\Rightarrow x\in\left\{0;\pm1;\pm2;\pm3;\pm4;\pm5;\pm6\right\}\)
\(\left|x\right|>7\Rightarrow\left[{}\begin{matrix}x>7\\x< -7\end{matrix}\right.\)