a.\(\left|9+x\right|=2x\)
\(ĐK:x\ge0\)
\(\Leftrightarrow\left[{}\begin{matrix}9+x=2x\\-9-x=2x\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}x=9\left(tm\right)\\x=-3\left(ktm\right)\end{matrix}\right.\)
b.\(\left|x-1\right|=3x+2\)
\(ĐK:x\ge-\dfrac{2}{3}\)
\(\Leftrightarrow\left[{}\begin{matrix}x-1=3x+2\\1-x=3x+2\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{3}{2}\left(ktm\right)\\x=-\dfrac{1}{4}\left(tm\right)\end{matrix}\right.\)
c.\(\left|x+6\right|=2x+9\)
\(ĐK:x\ge-\dfrac{9}{2}\)
\(\Leftrightarrow\left[{}\begin{matrix}x+6=2x+9\\-x-6=2x+9\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}x=-3\left(tm\right)\\x=-5\left(ktm\right)\end{matrix}\right.\)
d.\(\left|7-x\right|=5x+1\)
\(ĐK:x\ge-\dfrac{1}{5}\)
\(\Leftrightarrow\left[{}\begin{matrix}7-x=5x+1\\x-7=5x+1\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}x=1\left(tm\right)\\x=-2\left(ktm\right)\end{matrix}\right.\)
