Question

\(CMR\)

\(\left|a\right|< x\Rightarrow a< x;a>-x\left(x>0\right)\)

Answer 1

\(\left|a\right|=\hept{\begin{cases}a\Leftrightarrow a\ge0\\-a\Leftrightarrow a< 0\end{cases}}\)

=> |a|<x

=> a<x hoặc a>-x

Answer 2

TH1:\(\left|a\right|=a\Rightarrow a>0>x\)

\(a=\left|a\right|< x\Leftrightarrow a< x\)

Vậy \(a< x;a>-x\)

TH2:\(\left|a\right|=-a\Rightarrow0>-a>-x\)

 \(\Leftrightarrow\left|-a\right|< \left|-x\right|\Rightarrow a< x\)

Mà \(a>-a>-x\Leftrightarrow a>-x\)

Vậy \(a< x;a>-x\)