$$\color{rgb(0,0,0)}y=x+1$$

$$\color{rgb(255,0,0)}C_1$$

$$\color{rgb(0,127,0)}C$$

$$\color{rgb(127,0,127)}C_k$$

$$\color{rgb(0,0,0)}\begin{array}{l} A\left( 1;\frac{1}{3} \right) \\ B\left( 1;\frac{5}{3} \right) \end{array}$$

$$\color{rgb(0,0,0)}y=x-1$$

$$\color{rgb(0,0,255)}C'$$