2. A linear function is a function whose graph is a line. 
A linear function is a function whose graph is a line.  changes by a constant amount

3. Remember … You can write any linear function in the form

4. b is the y-intercept . starting point . initial value 
b is the y-intercept  starting point  initial value  amount prior to any change

5.  fixed expenses  base salary  set-up charges

6. m is the slope . steady change . how much the result
m is the slope  steady change  how much the result changes over regular intervals

7.  variable expenses  bonus pay Any sort of dependent change (look for “per”) is usually given by the slope.

8. In the real world we most often see relationships that are APPROXIMATELY (but not exactly) linear.

9. We can use linear models as a way of finding good estmates for values we don’t know.

10. Extrapolation Estimating values beyond those we know.

11. When we extrapolate, we assume a pattern will continue.

12. Interpolation Estimating values between those we already know

13. When we interpolate, we assume all points are on a straight line (nothing weird happens in the middle).

14. It’s important to realize that interpolation and extrapolation are ESTIMATES.  They sometimes can give misleading and even silly answers.