Cho hàm số $f\left( x \right)$ có đạo hàm ${f}'\left( x...

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$\Leftrightarrow \left[ \begin{aligned}
& x=3 \\
& 2{{x}^{2}}-12x+m=0 \\
& 2{{x}^{2}}-12x+m=4 \\
& 2{{x}^{2}}-12x+m=-1 \\
\end{aligned} \right.$$\Leftrightarrow \left[ \begin{aligned}
& x=3 \\
& 2{{x}^{2}}-12x+m=0 \left( 1 \right) \\
& 2{{x}^{2}}-12x+m-4=0 \left( 2 \right) \\
& 2{{x}^{2}}-12x+m+1=0 \left( 3 \right) \\
\end{aligned} \right.\Leftrightarrow \left\{ \begin{aligned}
& {{{{\Delta }'}}_{\left( 1 \right)}}>0 \\
& {{2.3}^{2}}-12.3+m\ne 0 \\
& {{{{\Delta }'}}_{\left( 2 \right)}}>0 \\
& {{2.3}^{2}}-12.3+m-4\ne 0 \\
\end{aligned} \right. \Leftrightarrow \left\{ \begin{aligned}
& 36-2m>0 \\
& m\ne 18 \\
& 36-2\left( m-4 \right)>0 \\
& m\ne 22 \\
\end{aligned} \right. \Leftrightarrow \left\{ \begin{aligned}
& m<18 \\
& m\ne 18 \\
& m<22 \\
& m\ne 22 \\
\end{aligned} \right. \Leftrightarrow m<18mm\in \left\{ 1;2;3;...;17 \right\}$.