Science:Math Exam Resources/Courses/MATH105/April 2012/Question 01 (c)/Hint 1

First, use the fact from part (b) that

${\frac {1}{1-r}}=1+r+r^{2}+r^{3}+\dots$

provided |r| < 1, to get the power series of $\ln(1-r)$ per integration. Then make a proper substitution for r.