Science:Math Exam Resources/Courses/MATH105/April 2014/Question 06 (b)/Hint 3

Consider writing out the terms of $-\ln a_1+\sum _{n=1}^k\ln (\frac{a_n}{a_{n+1}})$ for a general k. You may find it useful to recall $\ln (x/y)=\ln x-\ln y$. You should find many terms cancel.