Expanding and factorising · Year 9
In Year 9 you learn: expanding double brackets.
Expanding removes brackets by multiplying every term inside by what is outside. Factorising does the opposite: it puts brackets back in by taking out common factors. Both are everyday tools for simplifying algebra and solving equations.
Key facts
- Expand a single bracket by multiplying every term inside: 3(2x − 5) = 6x − 15.
- (a + b)² = a² + 2ab + b² — not a² + b².
Worked examples
Example 1
Expand (x + 4)(x − 7).
Answer: x² − 3x − 28