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 <= 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.