4MA1/1H Jun 2025, Question 15: Arithmetic series
Pearson Edexcel International GCSE Mathematics A 4MA1 · Paper 1H (Higher) · Calculator · 4 marks
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The question, in short
Solve (5a + 8)/3 − (2a + 5)/4 = 23, then write (√y ÷ 3)⁻¹ in the form cyⁿ.
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Part (a) · 1 mark
Solve (5a + 8)/3 − (2a + 5)/4 = 23.
- 1(√3)⁵ = (√3)² × (√3)² × √3
- 2= 3 × 3 × √3 = 9√3
- 3k = 9
Answer9
Part (b) · 3 marks
Write (√y ÷ 3)⁻¹ in the form cyⁿ.
- 1Multiply by (3 + √2)/(3 + √2)
- 2Denominator: (3 − √2)(3 + √2) = 9 − 2 = 7
- 3Numerator: 21(3 + √2) = 63 + 21√2
- 4(63 + 21√2)/7 = 9 + 3√2
- 53√2 = √18, so 9 + √18 (c = 9, d = 18)
Answer9 + √18
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