IGCSE Mathematics Foundation: Algebraic Manipulation

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Algebraic Manipulation builds on earlier work with number and the order of operations by introducing the language and methods of algebra. This unit develops the skill of simplifying and rewriting expressions.

Students learn to substitute using the order of operations, collect like terms and simplify products. They then expand and factorise linear expressions, before expanding two brackets, leaving solving equations and factorising quadratics for later units.

What Success Looks Like

By the end of this unit students will be able to:

  • Substitute directed numbers using the order of operations, including a power.
  • Collect like terms and leave unlike terms uncombined.
  • Expand a single bracket, including a negative multiplier, without dropping the second term.
  • Factorise to the highest common factor, including a power, and expand two binomials collecting the linear terms.

Prerequisite Knowledge

Students should be secure with the following before beginning this unit.

  • Use the order of operations when a calculation includes a power or a bracket.
  • Multiply and divide directed numbers, including two negatives.
  • Write a missing-number problem using a letter.
  • Find the highest common factor of two integers.

Key Mathematical Ideas

Notation

The multiplication sign is dropped, so ab means a × b. Division is written as a fraction. A coefficient of 1 is not written. 2a means 2 × a, not 2 + a.

Like terms

Only terms with the same letter and the same power can be collected. 3x and 3x² are not like terms. ab and ba are like terms.

Expanding brackets

Every term inside the bracket is multiplied. 3(a + b) is 3a + 3b and −2(x + 5) is −2x − 10. Two brackets need four products, then the linear terms are collected.

Highest common factor

Factorising is not finished until the highest common factor of the numbers and the letters has been taken out. 18x + 24y is 6(3x + 4y), not 2(9x + 12y).

Working Mathematically

Fluency

  • Substitute a = 2 and b = −3 into 3a + 2b².
  • Simplify 4a + 3b − a + 5b, then expand 3(2x − 5).
  • Factorise 12x + 18 and expand (x + 4)(x − 3).

Reasoning

  • Explain why 2x and 2x² cannot be collected.
  • Show that 18x + 24y is not fully factorised if the common factor is taken to be 2.
  • Check (x + 4)(x − 3) by substituting x = 2 into both the product and the expanded form.

Common Misconceptions with Algebraic Manipulation

MisconceptionTeaching focus
Treating 2a as 2 + a, or writing a + b as ab.Substitute a = 3 and b = 4 into both forms so students can see they are equal or not.
Collecting 3x and 3x², or treating ab and ba as unlike terms.Write the power next to each letter before any collecting starts.
Multiplying only the first term in a bracket, especially when the multiplier is negative.Draw two arrows from the term outside onto every term inside, including the sign.
Stopping factorising at a common factor that is not the highest, so 4x + 8 becomes 2(2x + 4).Check the bracket: if the numbers inside still share a factor, the work is not finished.
Expanding (x + 2)(x + 3) as x² + 6, missing the two middle products.Use an area grid so all four products are visible before like terms are collected.

Differentiation

Additional support

  • Write the substitution in a vertical list, one operation per line, for the first lesson.
  • Give the common factor of 18x + 24y and ask only for the contents of the bracket.
  • Use an area grid for the first two-bracket expansion.

Additional challenge

  • Substitute a = −2 into (3a + 1) / a and simplify the numerical answer.
  • Factorise 12x²y + 18xy² and state the highest common factor of the coefficients and the letters.
  • Expand (x + 2)(x + 5) and check by substituting x = −2 into both forms.

Teach This Unit with Mr Mathematics

Every lesson in this unit is already built. A Mr Mathematics membership gives you the presentation, worksheet, question generator and video tutorial for all seven lessons, alongside the full Key Stage 3, GCSE, IGCSE and A-Level libraries.

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Algebraic Manipulation Lessons


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