1. The problem is to understand the notation \overleftrightarrow{AC}, which represents a line passing through points A and C. 2. In geometry, the notation \overleftrightarrow{AC} means the infinite line that extends in both directions through points A and C. 3. This line includes all points between A and C and beyond in both directions. 4. If coordinates of points A and C are known, the equation of the line can be found using the slope formula and point-slope form. 5. For example, if A=(x_1,y_1) and C=(x_2,y_2), the slope $m$ is given by: $$m=\frac{y_2 - y_1}{x_2 - x_1}$$ 6. Then the line equation in point-slope form is: $$y - y_1 = m(x - x_1)$$ 7. This equation represents the line \overleftrightarrow{AC}. Since no coordinates are given, this is the general explanation of the notation and how to find the line equation if needed.