Expanding Brackets (OCR AS Maths: Pure)

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Expanding Brackets

What do I need to know about expanding brackets?

  • To expand brackets, the rule is that each term in one set of brackets must be multiplied by each term in the other set of brackets

2.5.1 Expanding Brackets Illustration, Edexcel A Level Maths: Pure revision notes 

  • 'FOIL' is a special case of this, when each set of brackets contains two terms you can mulitply in order
    • e.g. to multiply out or expand these brackets (2x + 3)(x - 5)
      • First (2x + 3)(x - 5) gives 2x2
      • Outside (2x + 3)(x - 5) gives -10x
      • Inside (2x + 3)(x - 5) gives +3x
      • Last (2x + 3)(x - 5) gives -15
    • (2x + 3)(x - 5) = 2x2 -10x +3x -15 = 2x2 -7x -15
  • If you spot something like (a + b)2 or (a + b)3 just write the brackets out twice or three times respectively
    • e.g. (3x + 2)2 = (3x +2)(3x+2) = 9x2 + 6x + 6x + 4 = 9x2 + 12x + 4
  • If you are trying to expand something like (a + b)n for powers of n greater than 2 or 3, use the binomial expansion
  • If you have to expand more than two sets of brackets, just expand them two at a time

Worked example

2.5.1 Expanding Brackets Example, Edexcel A Level Maths: Pure revision notes

Worked example

2.5.1 Expanding Brackets Multiple, Edexcel A Level Maths: Pure revision notes

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Roger

Author: Roger

Expertise: Maths

Roger's teaching experience stretches all the way back to 1992, and in that time he has taught students at all levels between Year 7 and university undergraduate. Having conducted and published postgraduate research into the mathematical theory behind quantum computing, he is more than confident in dealing with mathematics at any level the exam boards might throw at you.