Tips: type <= for ≤, >= for ≥, abs(x-3) or |x-3| for absolute value. Use and/or. Multiplication shorthand like 2x is OK.
Examples
Number line
Open endpoints are hollow; closed endpoints are filled. Multiple segments indicate an OR (union).
What this supports (v1)
- Linear inequalities (each side can be any linear expression in x using +, −, ×, ÷, parentheses).
- Chained forms (e.g., a ≤ b < c), and explicit and/or connectors.
- Absolute values of the form |ax+b| ◊ k or abs(ax+b) ◊ k where k is a constant; solved via case-splitting.
- Domains ℝ, ℤ, ℕ. For ℤ/ℕ, interval results snap to the allowed integers.
Planned hooks exist in the code for polynomial/rational/sign-chart extensions.
FAQ
When does the inequality sign flip?
When multiplying or dividing by a negative number during isolation (e.g., −2x ≤ 6 becomes x ≥ −3).
How do chained inequalities work?
A chain like a ≤ b < c is equivalent to (a ≤ b) and (b < c). The calculator expands them and intersects results.
What about non-linear or rational inequalities?
v1 focuses on linear and basic absolute value cases. The code contains clear “TODO” markers where polynomial/rational sign-chart logic can be added.
How can I export the results?
Use “Copy results” to copy text; “Download number line (PNG)” for the plot; “Download sign table (CSV)” for quick test-point tables; or “Print” for a PDF.