4MA1/2H Jun 2021, Question 21: Stationary Points and Turning Points
Pearson Edexcel International GCSE Mathematics A 4MA1 · Paper 2H (Higher) · Calculator · 5 marks
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The question, in short
Curve y = kx² + 16/x has one stationary point A at (2/3, a). Find the value of a, showing working.
Summarised in our own words. Use the official paper for the exact wording and any diagrams.
Solution · 5 marks
- 1dy/dx = 2kx − 16/x²
- 2At the stationary point dy/dx = 0; at x = 2/3: 2k(2/3) − 16 ÷ (4/9) = 0
- 34k/3 − 36 = 0, so k = 27
- 4a = 27 × (2/3)² + 16 ÷ (2/3) = 12 + 24
- 5a = 36
Answer36
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