



 
Hi Dave, Suppose I am thinking about a line and its slope is 2. Here are some possibilities. How can I tell you which line I am thinking about? I am going to tell you which one with an equation that I produce using the point (0, 5) where the line crosses the yaxis. Suppose (x, y) is some other point on the line. Since the slope of the line is 2 the slope of the line joining (0, 5) and (x, y) is 2. That is If I now multiply both sides by x I get
This is exactly the slope intercept form of the line, the slope is 2 and the yintercept is 5. I hope this helps,  


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