📘 Class 8 · Mathematics

Chapter 12: Factorisation

5 lessons

Factorisation reverses expansion — rewriting a sum of terms as a product of simpler factors, using common factors, the identities from Algebraic Expressions, and division of one expression by another. x²+8x+15, run through the identity backward, factors to (x+3)(x+5).

This is one of the most reused skills in all of secondary mathematics: it becomes the core method for solving quadratic equations two years later in Class 10, and a student who struggles here typically struggles there for exactly the same underlying reason.

1
Introduction to Factorisation
Common factors method and factorisation by grouping.
 2
Exercise 12.1 — Common Factors
Factorisation method and grouping the terms.
 3
Exercise 12.2 — Factorisation by Identities
Factorisation using algebraic identities.
 4
Exercise 12.3 — Division of Expressions
Division of algebraic expressions.
 5
Exercise 12.4 — Finding Errors
Finding and correcting errors in given equations.

The incomplete-answer trap

Stopping at a partial factorisation — pulling out a common factor but missing that the remaining bracket can be factorised further — is the most frequent mistake, more common than misapplying an identity outright.