Solid or Dashed

The boundary line is sometimes part of the solutions and sometimes not, like the endpoint of an interval on the number line. The inequality $y \le x+1$ includes its boundary line, so the line is drawn solid. The inequality $y < x+1$ does not include it, so the line is drawn dashed. A point on a dashed boundary satisfies the equation $y = x+1$ but not the strict inequality.

Choose the shaded side and decide whether the boundary is included. Use a solid line for ≤ or ≥, and a dashed line for < or >. These correspond to filled and open endpoints on a number line.