Question

Tìm x biết:

a) /x/ = 7

b) /x/ < 7

c) /x/ > 7

{gạch chéo trên là thẳng đấy ạ!}

Giúp mình với !!!

Answer 1

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

Answer 2

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....

Answer 3

\(\left|x\right|=7\) \(\Rightarrow\left[{}\begin{matrix}x=7\\x=-7\end{matrix}\right.\)

\(\left|x\right|< 7\Rightarrow x\in\left\{0;\pm1;\pm2;\pm3;\pm4;\pm5;\pm6\right\}\)

\(\left|x\right|>7\Rightarrow\left[{}\begin{matrix}x>7\\x< -7\end{matrix}\right.\)