# Sequences and Series

If you think dogs can't count, try putting three dog biscuits in your pocket and then giving Fido only two of them.

-- Phil Pastoret

In this chapter, we're going to look at some of the ways that the counting methods from the previous chapter can be applied both to real world problems and to making mathematical problems liking multiplying out polynomials easier.

## Technologies UsedWe try to limit the technologies that are used in each classroom to the minimum required to get the job done. The combinatorics classroom uses JavaScript which all modern browsers support and HTML5 to display videos. JavaScript shouldn't give you any trouble - all browsers going back many versions support everything we'll do with it. HTML5, on the other hand, is only supported by the more recent versions of most browsers. | ## Level of DifficultyThe first section of this chapter requires only multiplication, division and an understanding of the counting methods from Chapter 1. The second two sections also require an understanding of how to multiply polynomials. |