What are the values of a1 and r of the geometric series?

2 - 2 + 2 - 2 + 2

First term, a, is 2. Next term, - 2, is the product of 2 and - 1 and is - 2. Next term, 2, is the product of - 2 and - 1. Thus, the first term, a, is 2 and the common ratio, r, is - 1.