Q1
What is (a+b)²?
Aa² + 2ab + b²
Ba² + b²
Ca² - 2ab + b²
D2a + 2b
ICSEClass 9 (ICSE)MathematicsCh 4 · Topic 2
Practice and Revision - Expansions (Algebraic Identities)
Let us practise and revise what we learned about expansions (algebraic identities). Algebraic identities like (a+b)², (a-b)², and (a+b)(a-b)
Core concept
(a+b)² = a² + 2ab + b² and (a-b)² = a² - 2ab + b² are commonly used identities for expanding squared binomials.
How it works
(a+b)(a-b) = a² - b² is useful for quickly multiplying the sum and difference of the same two terms.
Why it matters
More advanced identities include (a+b+c)² = a² + b² + c² + 2ab + 2bc + 2ca, used for trinomial expansions.
Key detail
Mastering these identities significantly speeds up algebraic calculations and forms the basis for factorisation techniques.
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Quick notes
• (a+b)² = a² + 2ab + b².
• (a-b)² = a² - 2ab + b².
• (a+b)(a-b) = a² - b².
• (a+b+c)² expands with six terms.
• It includes squares and cross products.
• These identities speed up calculations.
• They form the basis for factorisation.
• Practice helps master these identities.