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Linear inequalities in one unknown・Form 3 maths

Solve a linear inequality

A standard method from Linear inequalities in one unknown: the steps and worked examples.

Steps

  1. Solve exactly like an equation: expand, move terms, collect.
  2. If you multiply or divide by a negative number, flip the sign.
  3. Draw the number line: hollow circle for > or <, solid dot for ≥ or ≤.
  4. For "greatest integer" or "least integer", read it off the number line.

Why the flip: 3 > 2, but −3 < −2. Multiplying by −1 swaps the order of numbers on the number line.

Safer habit: move the x-terms to the side where the coefficient stays positive, so you never divide by a negative.

Worked examples

Example 1: Solve the linear inequality 3 − 2x > 7.
−2x > 4
  x < −2      divide by −2, flip

For the whole topic, read Linear inequalities in one unknown: key points, common mistakes and how the DSE tests it.