Class 9 Mathematics Chapter 4 Exploring Algebraic Identities – Revision Notes

Quick revision notes for Class 9 Maths Chapter 4 (Exploring Algebraic Identities). These Class 9 Mathematics Chapter 4 notes are ideal for quick revision just before exams.

Standard Identities

• (a+b)² = a²+2ab+b²
• (a−b)² = a²−2ab+b²
• a²−b² = (a+b)(a−b)
• (x+a)(x+b) = x²+(a+b)x+ab
• (a+b)³ = a³+b³+3ab(a+b)
• (a−b)³ = a³−b³−3ab(a−b)
• a³+b³ = (a+b)(a²−ab+b²)
• a³−b³ = (a−b)(a²+ab+b²)

Uses

• Quick expansion (substitute into identity).
• Factorisation (recognise pattern, reverse identity).
• Mental calculation (e.g. 102×98 via difference of squares).

One-Line Summary

Algebraic identities are universally true equations that speed up expansion, factorisation, and even arithmetic by letting you substitute into known patterns instead of multiplying term by term.

Written by Satish

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