[tex]A(-1,1);\quad B(0,3);\quad C(1,5).\\ \\ \left\{\begin{aligned}m_{AB} &= \dfrac{3-1}{0-(-1)} = \dfrac{2}{1} = 2\\ \\ m_{AC} &= \dfrac{5-1}{1-(-1)} = \dfrac{4}{2} = 2\\ \\ m_{BC} &= \dfrac{5-3}{1-0} = \dfrac{2}{1} = 2 \end{aligned}\,\right| \Rightarrow m_{AB} = m_{AC} = m_{BC}\\ \\ \\ \Rightarrow A,B, C\text{ sunt coliniare.}[/tex]
