If you understand the definition of a mathematical function, a good way to judge it is that any line drawn parallel to the y-axis intersects with the values in the function’s curve only once. The same ...

Inequalities that use < or > symbols are plotted with a dashed line to show that the line is not included in the region. Inequalities that use ≤ or ≥ symbols are plotted with a solid line to show that ...