2.(x-3).(x-15) =0

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Đáp án:

`2 xx (x - 3) xx (x - 15) = 0`

`(x - 3) xx (x - 15) = 0 : 2`

`(x - 3) xx (x - 15) = 0`

\(\left[ \begin{array}{l}x - 3 = 0\\x - 15 = 0\end{array} \right.\) 

\(\left[ \begin{array}{l}x=0 + 3\\x=0 + 15\end{array} \right.\) 

\(\left[ \begin{array}{l}x=3\\x=15\end{array} \right.\) 

Vậy `x in {3;15}`