ĐKXĐ: \(x\ne-1\)
\(\left|\dfrac{x-1}{x+1}\right|=2\)
\(\Leftrightarrow\dfrac{x-1}{x+1}=2\) hay \(\dfrac{x-1}{x+1}=-2\)
\(\Leftrightarrow\dfrac{x-1}{x+1}=\dfrac{2\left(x+1\right)}{x+1}\) hay \(\dfrac{x-1}{x+1}=\dfrac{-2\left(x+1\right)}{x+1}\)
\(\Leftrightarrow x-1=2x+2\) hay \(x-1=-2x-2\)
\(\Leftrightarrow x-2x=2+1\) hay \(x+2x=-2+1\)
\(\Leftrightarrow x=-3\left(nhận\right)\) hay \(x=\dfrac{-1}{3}\left(nhận\right)\)
-Vậy \(S=\left\{-3;\dfrac{-1}{3}\right\}\)
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