Algebra › Section I · Quadratic equations and functions › Topic I.8
Quadratic inequalities
A quadratic equation asks where a parabola crosses the axis; a quadratic inequality asks where it lives above or below. The parabola's shape turns a sign question into a picture, and the algebra needs only two numbers to draw it.
In this topic
- The question a quadratic inequality asks
- Critical values chop the line
- Test one point per zone
- Worked example: a full algebraic solve
- Strict or inclusive: brackets do the talking
- When the parabola never crosses
- Worked example: all-or-nothing, downward case
- Two intervals, or one, or none, or all
- Common mistakes to avoid
- Key takeaways
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