D mijlocul [AB]=>[tex]\left \{ {{x_D=\frac{x_A+x_B}{2} } \atop {y_D=\frac{y_A+y_B}{2}}} \right. \left \{ {{x_D=\frac{5-1}{2} } \atop {y_D=\frac{1+3}{2} }} \right. <=>\left \{ {{y_D=2} \atop {x_D=2}} \right.=>D(2,2)[/tex]
Fie M mijlocul [CD]=>[tex]\left \{ {{M_D=\frac{x_C+x_D}{2} } \atop {y_M=\frac{y_C+y_D}{2}}} \right. \left \{ {{x_M=\frac{8+2}{2} } \atop {y_M=\frac{10+2}{2} }} \right. <=>\left \{ {{x_M=5} \atop {y_M=6}} \right. =>M(5,6)[/tex]
[tex]m_{AC}=\frac{y_C-y_A}{x_C-x_A}=\frac{10-1}{8-5}=\frac{9}{3}=3[/tex]
[tex]d||AC=>m_d=m_{AC}=3\\[/tex][tex]d:y-y_M=m_d(x-x_M)<=>d:y-6=3(x-5)<=>d:y-6=3x-15=>d:y=3x-9[/tex]
