Science:Math Exam Resources/Courses/MATH105/April 2012/Question 08 (a)/Hint 1

By a visual inspection, we see that the terms that don't match up to the expression for $\arctan(x)$ are the terms corresponding to $x^{2n+1}$ and to $3^{-n}=(3^{-1})^{n}$ (moving the denominator up to the numerator). Thus, we want to get these two terms to match. How can we rearrange these terms to achieve this goal?