a/ \(19⋮3-n\)
\(\Leftrightarrow3-n\inƯ\left(19\right)\)
\(\Leftrightarrow\left[{}\begin{matrix}3-n=1\\3-n=19\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}n=2\left(tm\right)\=-22\left(loại\right)\end{matrix}\right.\)
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b/ \(21⋮1-2n\)
\(\Leftrightarrow1-2n\inƯ\left(21\right)\)
\(\Leftrightarrow\left[{}\begin{matrix}1-2n=1\\1-2n=21\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}n=0\=-10\left(loại\right)\end{matrix}\right.\)
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c/ \(9⋮\left|n-1\right|\)
\(\Leftrightarrow\left|n-1\right|\inƯ\left(9\right)\)
\(\Leftrightarrow\left[{}\begin{matrix}\left|n-1\right|=9\\\left|n-1\right|=3\\\left|n-1\right|=1\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}\left[{}\begin{matrix}n-1=9\-1=-9\end{matrix}\right.\\\left[{}\begin{matrix}n-1=3\-1=-3\end{matrix}\right.\\\left[{}\begin{matrix}n-1=1\-1=-1\end{matrix}\right.\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}\left[{}\begin{matrix}n=10\=-8\left(lọai\right)\end{matrix}\right.\\\left[{}\begin{matrix}n=4\=-2\left(loại\right)\end{matrix}\right.\\\left[{}\begin{matrix}n=2\=0\end{matrix}\right.\end{matrix}\right.\)
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d/ \(-15⋮3-2n\)
\(\Leftrightarrow3-2n\inƯ\left(-15\right)\)
\(\Leftrightarrow\left[{}\begin{matrix}3-2n=1\\3-2n=15\\3-2n=3\\3-2n=5\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}n=1\=-6\left(loại\right)\=0\=-1\left(loại\right)\end{matrix}\right.\)
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