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A-LevelMathematicsAlgebra9709/21 · Oct/Nov 2020 · Q45 Marks

Solve the equation |2x – 5| = |x + 6|.

  1. (a)Solve the equation |2x – 5| = |x + 6|.[3]
  2. (b)Hence find the value of y such that |2¹⁻ʸ – 5| = |2⁻ʸ + 6|. Give your answer correct to 3 significant figures.[2]

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2020). The mark or mark type is shown in brackets.

  1. [B1] State or imply non-modulus equation (2x-5)²=(x+6)² or pair of linear equations
  2. [M1] Attempt solution of 3-term quadratic equation or of pair of linear equations
  3. [A1] Obtain 1/3 and 11
  4. [M1] Apply logarithms and use power law for 2^-y = k where k > 0 from (a)
  5. [A1] Obtain -3.46 AWRT

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About this question

Topic
Algebra, A-Level Mathematics (syllabus 9709). Structured question, 5 marks.
Source
A-Level Mathematics, Oct/Nov 2020 Paper 2 Variant 1, question 4.

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