What is a quadratic inequality?

1. A quadratic equation sets a quadratic expression equal to 0. 2. Replacing the equal sign with an inequality sign gives a quadratic inequality. 3. Its standard form collects everything on one side against 0, as with the equation. 4. The solution is usually an interval or a union of two intervals rather than a short list. _Source: OpenStax Intermediate Algebra (CC BY 4.0), section 9.8 Solve Quadratic Inequalities_