-Hướng dẫn làm 1 bài, các bài khác làm tương tự.
b) \(\left|3x+2\right|-\left|7x+1\right|=0\)
\(\Leftrightarrow\left|3x+2\right|=\left|7x+1\right|\)
\(\Leftrightarrow\left(3x+2\right)^2=\left(7x+1\right)^2\)
\(\Leftrightarrow\left(3x+2\right)^2-\left(7x+1\right)^2=0\)
\(\Leftrightarrow\left[{}\begin{matrix}3x+2+7x+1=0\\3x+2-7x-1=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}10x+3=0\\-4x+1=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{-3}{10}\\x=\dfrac{1}{4}\end{matrix}\right.\)
-Vậy \(S=\left\{\dfrac{-3}{10};\dfrac{1}{4}\right\}\)
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