3.31: Logarithmic AP inequality and 25th term

0606/22/M/J/25 — Question 7 · 9 marks

(a)
The first three terms of an arithmetic progression can be written as 2ln(x3)2\mathrm{ln}(x^{3}), 5ln(x2)5\mathrm{ln}(x^{2}), 2ln(x7)2\mathrm{ln}(x^{7}), where x>1x>1. Find the least number of terms for the sum of this progression to be greater than 1032lnx1032\mathrm{ln}\,x.
[6]
(b)
Given the 2525th term equals 408408, find the exact value of xx.
[3]