\(\dfrac{3x}{x-3} (\text{ĐK:}x \not =3)\)
\(\text{Ta có: }3x=3(x-3)+9\)
\(\text{Ta có: }3(x-3)\ \vdots\ (x-3)\)
\(\text{Để }3x\ \vdots\ (x-3)\text{ thì }9\ \vdots\ (x-3)\)
\(\Rightarrow (x-3)\in Ư(9)=\{\pm1\ ;\pm3\ ;\pm9\}\)
\(\text{Lập bảng}\)
| \(x-3\) |
\(-9
\) |
\(-3\) |
\(-1\) |
\(1
\) |
\(3
\) |
\(9\) |
| \(x\) |
\(-6\) |
\(0\) |
\(2\) |
\(4\) |
\(6\) |
\(12\) |
\(\text{Vậy }x\in\{-6;0;2;4;6;12\}\)
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