a) \(\left|x\right|=\dfrac{3}{7}\)
\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{-3}{7}\\x=\dfrac{3}{7}\end{matrix}\right.\)
Vậy \(x\in\left\{\dfrac{3}{7};\dfrac{-3}{7}\right\}\)
b) \(\left|x\right|=0\)
\(\Rightarrow x=0\)
Vậy x=0
c) \(\left|x\right|=-8,7\)
Vì \(\left|x\right|\ge0\)
\(\Rightarrow x=\varnothing\)