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4PM1/01R Jan 2022, Question 8: Tangents, Normals and Stationary Points (Further)

Pearson Edexcel International GCSE Further Pure Mathematics 4PM1 · Paper 1R · Calculator · 8 marks

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The question, in short

For curve y = 2x² − sin x, find the gradient at x = π and show the normal at A has equation x + (4π + 1)y − π(8π² + 2π + 1) = 0.

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Solution · 8 marks

  1. 1At x = π: y = 2π² − sin π = 2π²
  2. 2dy/dx = 4x − cos x
  3. 3At x = π: dy/dx = 4π − cos π = 4π + 1
  4. 4Gradient of normal = −1/(4π + 1)
  5. 5y − 2π² = −(x − π)/(4π + 1)
  6. 6(4π + 1)(y − 2π²) = −x + π
  7. 7x + (4π + 1)y − 8π³ − 2π² − π = 0
  8. 8x + (4π + 1)y − π(8π² + 2π + 1) = 0

AnswerNormal x + (4π + 1)y − π(8π² + 2π + 1) = 0 shown

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