Reading inequalities

An inequality uses <, ≤, > or ≥ instead of =. It describes a range of values rather than a single answer.

2x + 1 < 9

means "any x for which 2x + 1 is strictly less than 9".

The one twist

You may add, subtract, multiply, or divide both sides — but if you multiply or divide by a negative number, the inequality flips.

Example: −2x ≤ 6. Divide by −2 and flip → x ≥ −3.

Graphing on a number line

• < and > use an open circle.
• ≤ and ≥ use a filled circle.
• Shade the side that satisfies the inequality.