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A-LevelMathematicsLogarithmic and exponential functions9709/22 · Oct/Nov 2020 · Q25 Marks

Given that 2³ˣ⁺² + 8 2³ˣ - 7 to 4 significant figures. = 5, find the value of 2³ˣ and hence, using logarithms, find the value of x correct

  1. (a)Given that 2³ˣ⁺² + 8 2³ˣ - 7 to 4 significant figures. = 5, find the value of 2³ˣ and hence, using logarithms, find the value of x correct[5]

Mark scheme

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

  1. [1] Use 2³ˣ⁺²=4×2³ˣ
  2. [1] Solve equation for 2³ˣ
  3. [1] Obtain 2³ˣ = 43
  4. [1] Apply logarithms and use power law for 2³ˣ = k where k>0
  5. [1] Obtain 1.809

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About this question

Topic
Logarithmic and exponential functions, A-Level Mathematics (syllabus 9709). Structured question, 5 marks.
Source
A-Level Mathematics, Oct/Nov 2020 Paper 2 Variant 2, question 2.

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