In geometry, we work with the undefined terms points, lines and planes. Words are usually defined by using known words to define an unknown word. We accept these three terms to be undefined as they have no formal definitions and are the building blocks for much of what we will learn in this course.
A review of slope. Including 2 examples of finding slope.
Source: http://patrickjmt.com/
Feel free to stop the video after 2 minutes.
Source: http://www.mathbyfives.com/