Inequality Calculator

Move everything to one side, find where the quadratic equals zero, then use a sign chart between and outside those roots. For x² − 4 < 0 the roots are −2 and 2, and the expression is negative between them, so the solution is (−2, 2). The sign only changes at a root, so testing one point in each interval tells you the sign across the whole interval.

Interval notation writes a solution set as ranges. A round bracket ( or ) excludes an endpoint (for < or >); a square bracket [ or ] includes it (for ≤ or ≥); ∪ joins separate pieces. For example, the solution to x² < 4 is written (−2, 2), and x ≤ −1 or x > 3 is written (−∞, −1] ∪ (3, ∞).

When you multiply or divide both sides by a negative number. This calculator avoids that pitfall by moving everything to one side and using a sign chart instead. For example, −2x > 6 becomes x < −3 once you divide by −2 and flip the sign.

No — the inequality calculator runs entirely in your browser using JavaScript, with no server round-trip. Nothing you type is uploaded, logged or stored. The calculator keeps working without an internet connection.