$M \in \Delta \Rightarrow M(2a+1;a)$
Ta có $\overrightarrow{MA}-2\overrightarrow{MB}+3\overrightarrow{MC}=(4-4a;-2a+8)$$\left| {\overrightarrow{MA}-2\overrightarrow{MB}+3\overrightarrow{MC}} \right|=\sqrt{(4-4a)^{2}+(-2a+8)^{2}}=\sqrt{20a^{2}-64a+80}$
$\left| {\overrightarrow{MA}-2\overrightarrow{MB}+3\overrightarrow{MC}} \right|$$_{min}\Leftrightarrow (20a^2-64a+80)_{min}$
Mà $(20a^2-64a+80)_{min}=\frac{144}{5}$ khi $a=\frac{8}{5}\Rightarrow M(\frac{21}{5};\frac{8}{5})$
Vậy $M(\frac{21}{5};\frac{8}{5})$