Algebra 1 · Inequalities
Closed Circle
Algebra 1 · Inequalities
Definition
A closed circle is a filled-in dot on a number line showing the boundary value is part of the solution.
Examples
- x ≥ 4 uses a closed circle at 4.
- x ≤ −1 uses a closed circle at −1.
Key rule
Use a closed circle for ≤ and ≥.
Memory hook
Closed circle = included; the line touches it.