Expanding brackets and factorising
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The teaching part (1 min) is free to watch. A free account opens the whole lecture: 7 practice questions, 1 real past-paper question with the answer explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- Two ways of writing the same thing
- A single bracket
Read the transcript of the teaching part
Last time
Before we start: last time, in Currency, money problems and time, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
Two ways of writing the same thing
Three lots of x plus four is three x plus twelve. Going from the bracket to the long form is called expanding. Going back is called factorising. They are opposites, like multiplying and dividing. Today you do both, from single brackets to quadratics.
A single bracket
To expand a bracket, multiply every term inside by the term outside. Do not leave any out. Three times two x minus five. Three times two x is six x. Three times minus five is minus fifteen. A minus sign outside changes every sign inside. Minus two times x minus four is minus two x plus eight. Put them together and collect: six x minus two x is four x, and minus fifteen plus eight is minus seven.
How often it comes up
How often Cambridge has asked each part, counted by ExamYard from every past paper in its question bank: Expanding and simplifying · Factorising expressions.
The whole chapter: Algebraic Manipulation.
Chapter 8: Algebra
- Simplifying, substituting and forming expressions 5 min
- Expanding brackets and factorising 5 min
Also for O Level Maths 4024
Which topics come up most in O Level Maths 4024 past papers, counted from every paper since 2004.