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Chapter 3 of 10

📐 Algebra & Equations

7 min+20 XP

Algebra is the highest-weightage topic in E-Math, appearing in both papers and forming the foundation for many other topics including graphs, trigonometry, and statistics. You must master algebraic manipulation, factorisation, quadratic equations, simultaneous equations, algebraic fractions, and inequalities. This chapter provides comprehensive coverage with multiple worked examples for every key technique.

Algebraic fluency is what separates A1 students from the rest. Many students understand the concepts but lose marks because they make errors during manipulation. The key to mastery is practice — work through every example in this chapter, then attempt past paper questions until the techniques become second nature.

Algebraic Expansion & Identities

Expansion means removing brackets by multiplying each term inside the bracket by the term outside. For two binomials, use the FOIL method (First, Outer, Inner, Last) or the grid method. However, the three special algebraic identities below are so commonly used that you should memorise them and apply them directly — this saves time and reduces errors.

Perfect Square (Sum)

(a + b)^2 = a^2 + 2ab + b^2

Perfect Square (Difference)

(a - b)^2 = a^2 - 2ab + b^2

Difference of Two Squares

(a + b)(a - b) = a^2 - b^2

The most common mistake with perfect squares is forgetting the middle term. Students write (a + b)^2 = a^2 + b^2, which is WRONG. The correct expansion always has the middle term 2ab. Always check your expansion by counting terms: a perfect square expansion should have 3 terms.

🧮Algebraic Expansion & Factorisation

Special algebraic identities tested frequently in Paper 1. Must be able to expand and factorise fluently.

Difference of two squares
a^2 - b^2 = (a + b)(a - b)
Perfect square (sum)
a^2 + 2ab + b^2 = (a + b)^2
Perfect square (difference)
a^2 - 2ab + b^2 = (a - b)^2
Cross multiplication method
ax^2 + bx + c = (px + q)(rx + s) \text{ where } pr = a,\, qs = c,\, ps + qr = b
Expansion of (a + b)(c + d)
(a + b)(c + d) = ac + ad + bc + bd
Expansion of (a + b)^3
(a + b)^3 = a^3 + 3a^2b + 3ab^2 + b^3

📝Worked Example 1: Using Algebraic Identities

Q
Question

Expand and simplify (3x + 2)^2 - (3x + 2)(3x - 2).

📝Worked Example 2: Expanding Three Brackets

Q
Question

Expand (x + 1)(x - 2)(x + 3).

🎯Key Takeaway
Algebra carries the most marks in E-Math. Know all four factorisation methods and all three quadratic equation methods. Always check solutions by substituting back. For inequalities, FLIP the sign when multiplying/dividing by a negative. For algebraic fractions, factorise denominators first. For changing the subject, collect terms with the target variable on one side and factor it out.

What the full chapter covers

  • Algebraic Expansion & Identities

  • Factorisation

  • Algebraic Fractions

  • Quadratic Equations — 3 Methods

  • Method 1: Factorisation

  • Method 2: Quadratic Formula

  • Method 3: Completing the Square

  • Simultaneous Equations

  • Inequalities

  • Changing the Subject of a Formula

  • Forming Equations from Geometric Contexts

  • Algebraic Word Problems

  • Discriminant Quick Guide

  • Critical Rule: Flipping the Inequality Sign

  • Algebra Study Plan

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