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O-LevelAdditional MathematicsQuadratic functions4037/12 · Oct/Nov 2013 · Q24 Marks

Find the set of values of k for which the curve y = (k + 1)x² – 3x + (k + 1) lies below the x-axis.

  1. Find the set of values of k for which the curve y = (k + 1)x² – 3x + (k + 1) lies below the x-axis.[4]

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2013). The mark or mark type is shown in brackets.

  1. [M1] Using b² – 4ac, 9 = 4 (k + 1)²
  2. [DM1] for solution of their quadratic in k
  3. [A1] for critical value(s), 5/2, -1/2, not necessary
  4. [A1] for k < -5/2 only
  5. Or:
  6. [M1] for a complete method to this point.

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About this question

Topic
Quadratic functions, O-Level Additional Mathematics (syllabus 4037). Structured question, 4 marks.
Source
O-Level Additional Mathematics, Oct/Nov 2013 Paper 1 Variant 2, question 2.

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