Simplifying Algebraic Expressions

Collect like terms, multiply expressions, and simplify algebraic fractions for GCSE Maths.

Simplifying algebraic expressions means collecting like terms and reducing expressions to their simplest form. This foundational skill is needed throughout GCSE Maths.

Core Concepts

Collecting Like Terms

Like terms have the same variable(s) raised to the same power.

3x+5x=8x3x + 5x = 8x

4x2+3x2x2+x=2x2+4x4x^2 + 3x - 2x^2 + x = 2x^2 + 4x

2xy+3x+xy=3xy+3x2xy + 3x + xy = 3xy + 3x (xy terms are like terms)

Multiplying Terms

Multiply coefficients and add powers:

3x×4x=12x23x \times 4x = 12x^2

2a2×5a3=10a52a^2 \times 5a^3 = 10a^5

2x×3x2=6x3-2x \times 3x^2 = -6x^3

Expanding Single Brackets

3(2x+4)=6x+123(2x + 4) = 6x + 12

2(x5)=2x+10-2(x - 5) = -2x + 10 (careful with the negative!)

Expanding Double Brackets

(x+3)(x+5)=x2+5x+3x+15=x2+8x+15(x + 3)(x + 5) = x^2 + 5x + 3x + 15 = x^2 + 8x + 15

Use FOIL: First, Outer, Inner, Last.

Dividing Terms

12x34x=3x2\frac{12x^3}{4x} = 3x^2

6a2b2ab=3a\frac{6a^2b}{2ab} = 3a

Worked Example: Example 1

Problem

Simplify 5x+3y2x+7y=3x+10y5x + 3y - 2x + 7y = 3x + 10y

Solution

Worked Example: Example 2

Problem

Expand (2x1)(3x+4)(2x - 1)(3x + 4) =6x2+8x3x4=6x2+5x4= 6x^2 + 8x - 3x - 4 = 6x^2 + 5x - 4

Solution

Worked Example: Example 3

Problem

Simplify 8x2y4xy2=2xy\frac{8x^2y}{4xy^2} = \frac{2x}{y}

Solution

Common Mistakes

  • Adding unlike terms. 3x+2x25x33x + 2x^2 \neq 5x^3.
  • Sign errors when expanding brackets. 2(x3)=2x+6-2(x - 3) = -2x + 6, not 2x6-2x - 6.
  • Forgetting to multiply all terms inside the bracket.

Practice Problems

    1. Simplify 4a+3b2a+5b4a + 3b - 2a + 5b.
    1. Expand 3(2x7)-3(2x - 7).
    1. Expand and simplify (x4)(x+6)(x - 4)(x + 6).
    1. Simplify 15x35x\frac{15x^3}{5x}.

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Key Takeaways

  • Like terms have the same variables and powers.

  • Expanding: multiply every term inside by every term outside.

  • FOIL for double brackets.

  • Watch out for negative signs when expanding.

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