||x + 5| - 4| = 3
+ TH1: \(\left|x+5\right|-4=3.\)
\(\Rightarrow\left|x+5\right|=3+4\)
\(\Rightarrow\left|x+5\right|=7.\)
\(\Rightarrow\left[{}\begin{matrix}x+5=7\\x+5=-7\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=7-5\\x=\left(-7\right)-5\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=2\\x=-12\end{matrix}\right.\)
+ TH2: \(\left|x+5\right|-4=-3.\)
\(\Rightarrow\left|x+5\right|=\left(-3\right)+4\)
\(\Rightarrow\left|x+5\right|=1.\)
\(\Rightarrow\left[{}\begin{matrix}x+5=1\\x+5=-1\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=1-5\\x=\left(-1\right)-5\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=-4\\x=-6\end{matrix}\right.\)
Vậy \(x\in\left\{2;-12;-4;-6\right\}.\)
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