This video will show you everything you ever needed to know about families of straight lines. It's part of the Methods 1 and 2 course here in Australia, but it is equally valid for all maths courses the world over. The video deals with the following topics:
Know what makes it means to have a family of straight lines
Know the three families of straight lines which are used in the textbook series
There are a number of worked examples provided to scaffold the theory and some useful exam hints and tips.