a) \(3x⋮x-2\)
ta có \(x-2⋮x-2\)
\(\Rightarrow3\left(x-2\right)⋮x-2\)
\(\Rightarrow3x-6⋮x-2\)
mà \(3x⋮x-2\)
\(\Rightarrow3x-\left(3x-6\right)⋮x-2\)
\(\Rightarrow3x-3x+6\) \(⋮x-2\)
\(\Rightarrow6\) \(⋮x-2\)
\(\Rightarrow x-2\in\text{Ư}_{\left(6\right)}=\text{ }\left\{1;2;3;6\right\}\)
+) nếu \(x-2=1\Rightarrow x=3\) ( thỏa mãn )
+) nếu \(x-2=2\Rightarrow x=4\) ( thỏa mãn )
+) nếu \(x-2=3\Rightarrow x=5\) ( thỏa mãn )
+) nếu \(x-2=6\Rightarrow x=8\) ( thỏa mãn )
vậy \(x\in\text{ }\left\{3;4;5;8\right\}\)
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