Expanding single brackets

Tier: #Foundation #Higher

🔗What you need to know first
How to

Multiplying terms within a bracket by the term in front. This process is the reverse of Basic factorising

e.g. $3(x+2)=3x+6$

You multiply everything inside the brackets by the term in front of the brackets. In the above case, $x$ is multiplied by 3 as is 2.

$2x(3x-4)=6x^2-8x$

Students often get caught out if there is a minus sign in front:

$-3(x-4)=-3x+12$

Especially if it's in the middle of an expression:

$2(x+3)-4(x-5)=2x+6-4x+20$

The final '+20' is missed a significant number of times!

Questions to practise

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📝Past paper questions
💬What the examiners say
  • "Most students scored full marks. However, a significant number of students gave the correct answer in the working space but then misguidedly tried to "simplify" the expression by combining the two terms."
⬆️How you can quickly improve
  • Apply the index law explicitly when multiplying: xᵃ × xᵇ = x^(a+b), including when one of the indices is negative.
  • After expanding, check whether the remaining terms are genuinely like terms before combining — only group terms with the same variable and power.
  • Multiply every term inside the bracket by the factor outside, and check the sign of each product individually.
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