GMAT Problem Solving Question 43: Sequences and summations

 
Try the following GMAT Problem Solving question that tests your ability to find the sum of the terms of a sequence.

Question 43:

Let $a_1$, $a_2$, $a_3$, $\ldots$, $a_n$, be a sequence of numbers where $a_1=-2$, $a_2=4$, and for $n \geq 3$, $a_n = \left(\dfrac{a_{n-1}}{a_{n-2}}\right)$. What is the sum of the first $99$ terms?

1. $\quad -16$

2. $\quad -12$

3. $\quad -8$

4. $\quad -4$

5. $\quad 0$