trung tuyến AM thuộc Ox\(\Rightarrow pt\left(AM\right):y=0\)
gọi A(a ; 0)\(\in\left(AM\right)\)
N là trung điểm AB\(\Rightarrow\left\{{}\begin{matrix}2x_N=1+a\\2y_N=1+0\end{matrix}\right.\left(1\right)\)
N \(\in\left(CN\right)\Rightarrow2x_N+4y_N-11=0\left(2\right)\)
Từ \(\left(1\right);\left(2\right)\Rightarrow a=8\Rightarrow A\left(8;0\right)\)\(\Rightarrow\overrightarrow{AB}=\left(-7;1\right)\Rightarrow\overrightarrow{n}=\left(1;7\right)\)
vay pt (AB) :7(x-1)+1(y-1) =0 \(\Leftrightarrow\)7x+y-8 = 0