a/ \(7x-18=-81\)
\(\Leftrightarrow7x=-81+18\)
\(\Leftrightarrow7x=-63\)
\(\Leftrightarrow x=-63:7\)
\(\Leftrightarrow x=-8\)
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b/ \(3-\left|2x+5\right|=-4\)
\(\Leftrightarrow\left|2x-5\right|=3-\left(-4\right)\)
\(\Leftrightarrow\left|2x-5\right|=7\)
\(\Leftrightarrow\left[{}\begin{matrix}2x-5=7\\2x-5=-7\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}2x=12\\2x=-2\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=6\\x=-1\end{matrix}\right.\)
Vậy ....
c/ \(\left|x-3\right|=0\)
\(\Leftrightarrow x-3=0\)
\(\Leftrightarrow x=3\)
Vậy ....
d/ \(x-5⋮3x+2\)
Mà \(3x+2⋮3x+2\)
\(\Leftrightarrow\left\{{}\begin{matrix}3x-15⋮3x+2\\3x+2⋮3x+2\end{matrix}\right.\)
\(\Leftrightarrow17⋮3x+2\)
\(\Leftrightarrow3x+2\inƯ\left(17\right)\)
\(\Leftrightarrow\left[{}\begin{matrix}3x+2=1\\3x+2=17\\3x+2=-1\\3x+2=-17\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{1}{3}\\x=5\\x=-1\\x=-\dfrac{19}{3}\end{matrix}\right.\)
Vậy ...
