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A-LevelMathematicsAlgebra9709/22 · Oct/Nov 2017 · Q24 Marks

It is given that x satisfies the equation |x + 1| = 4. Find the possible values of |x + 4| - |x - 4|.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2017). The mark or mark type is shown in brackets.

  1. [M1] Solve 3-term quadratic equation or a pair of linear equations
  2. [A1] Obtain x = -5 and x=3
  3. [M1] Substitute (at least) one value of x (less than 4) into |x+4|-|x-4|, showing correct evaluation of modulus and producing only one answer in each case
  4. [A1] Obtain -8 and 6 and no others

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About this question

Topic
Algebra, A-Level Mathematics (syllabus 9709). Structured question, 4 marks.
Source
A-Level Mathematics, Oct/Nov 2017 Paper 2 Variant 2, question 2.

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