Question

Which of the following is an infinite series?

Answer 1

Answer: Choice C)  2 - 6 + 18 - 54 + ...

Explanation:

The three dots or ellipses indicate the pattern goes on forever to infinity. So the answer is between choices A and C based on this alone. Choice A is a sequence while choice C is a series. A sequence is simply a list of values often in some kind of mathematical pattern. A series is where you add values from a sequence together. This distinction rules out choice A and makes choice C the answer.

Note: choice C is a geometric series with first term 2 and common ratio -3. The infinite series diverges because r = -3 is outside the range -1 < r < 1.