G là trọng tâm \(\Leftrightarrow\left\{{}\begin{matrix}0+4+x_C=3.\dfrac{7}{3}\\2+0+y_c=3.1\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x_c=3\\y_c=1\end{matrix}\right.\Rightarrow C\left(3;1\right)\)
Có: `\vec(BC) (-1;1)`
`=>` PT: `-1(x-4)+1(y-0)=0 <=> -x+y+4=0`