Find the fifth term of an=2(-1) n

The 5th answer in this series would be -2. 

We know this because in any problem where we have a base (2) being multiplied by a -1^n power, the numbers will simply alternate between positive 2 and negative 2. All of the even powers will be positive 2 and all of the odd numbers will be negative 2. See the work below. 

2(-1)(-1)(-1)(-1)(-1)
2 (1)(-1)(-1)(-1)
2(1)(1)(-1)
2(-1)
-2

So since 5 is odd, the answer is negative 2.