Read a linear graph

In y = mx + b, m is the change in y for each unit increase in x and b is the y-value when x is zero. A graph combines a starting amount with a constant rate of change.

Write units on both axes. A straight line model is useful only over the domain where its assumptions make sense. A phone bill cannot always be extrapolated indefinitely if pricing changes.

Try it yourself

Make a table for zero through five visits and plot the ordered pairs.