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0606/22 May/Jun 2025, Question 8: Definite Integrals and Areas

Cambridge IGCSE Additional Mathematics 0606 · Paper 22 (Calculator) · Calculator · 11 marks

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The question, in short

For the curve y = 15/x − 5/x², find A on the x-axis and the maximum B, then calculate the exact area between line AB and the curve.

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Solution · 11 marks

  1. 1A: 15/x − 5/x² = 0 gives x = 1/3
  2. 2dy/dx = −15/x² + 10/x³ = 0 gives x = 2/3; B is (2/3, 45/4)
  3. 3∫ (15/x − 5/x²) dx = 15 ln x + 5/x
  4. 4Area under curve from 1/3 to 2/3 = (15 ln(2/3) + 15/2) − (15 ln(1/3) + 15) = 15 ln 2 − 15/2
  5. 5Area of triangle under AB = (1/2) × (1/3) × 45/4 = 15/8
  6. 6Shaded area = 15 ln 2 − 15/2 − 15/8 = 15 ln 2 − 75/8

Answer15 ln 2 − 75/8

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