- 2067 Mangsir · 5 marks
Express J₄(x) in terms of J₁ and J₀
Short answer
Using J_{p+1}=(2p/x)J_p−J_{p−1} repeatedly yields J₄(x)=(48/x³−8/x)J₁(x)+(1−24/x²)J₀(x); the printed coefficient 3/x is a misprint.
Show that J₄(x) = (48/x³ − 3/x) J₁(x) + (1 − 24/x²) J₀(x). [Coefficient '3/x' as printed; scan unclear]
[Printed coefficient: 3/x of J₁. Working with the recurrence relation gives 8/x, so the 3/x appears to be a misprint; the identity is proved below with 8/x, i.e. J₄ = (48/x³ − 8/x)J₁ + (1 − 24/x²)J₀. Checked numerically at x = 2.3, where both sides equal 0.05560, while the 3/x version gives 1.229.]
Use the recurrence relation Jₚ₊₁ = (2p/x)Jₚ − Jₚ₋₁.
Step by step
J₂ = (2/x)J₁ − J₀ (p = 1)
J₃ = (4/x)J₂ − J₁ (p = 2)
= (4/x)[(2/x)J₁ − J₀] − J₁
= (8/x² − 1)J₁ − (4/x)J₀
J₄ = (6/x)J₃ − J₂ (p = 3)
= (6/x)[(8/x² − 1)J₁ − (4/x)J₀] − [(2/x)J₁ − J₀]
= (48/x³ − 6/x − 2/x)J₁ + (1 − 24/x²)J₀
Result: J₄(x) = (48/x³ − 8/x) J₁(x) + (1 − 24/x²) J₀(x).
The J₀ coefficient (1 − 24/x²) matches the printed form; only the J₁ coefficient differs (8/x, not 3/x).
✓ Answer checked by Claude Opus 5.5 (high effort)
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