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A-LevelMathematicsDifferentiation9709/12 · Feb/Mar 2020 · Q13 Marks

The function f is defined by f(x) = 1 3x + 2 + x² for x < -1.

  1. Determine whether f is an increasing function, a decreasing function or neither.[3]

Mark scheme

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

  1. [B2, 1, 0] f'(x)=[-(3x+2)-²]x[3]+[2x]
  2. [B1] <0 hence decreasing Dependent on at least B1 for f'(x) and must include < 0 or '(always) neg'

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About this question

Topic
Differentiation, A-Level Mathematics (syllabus 9709). Structured question, 3 marks.
Source
A-Level Mathematics, Feb/Mar 2020 Paper 1 Variant 2, question 1.

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