Đặt \(f\left(x\right)=x^2-4x+m\)
Để pt có 2 nghiệm thỏa mãn \(0< x_1< x_2< 3\)
\(\Rightarrow\left\{{}\begin{matrix}\Delta'>0\\f\left(0\right)>0\\f\left(3\right)>0\\0< \frac{S}{2}< 3\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}4-m>0\\m>0\\m-3>0\\0< 2< 3\end{matrix}\right.\) \(\Rightarrow3< m< 4\)