standard_description: Construct a function to model a linear relationship between two quantities. Determine the rate of change and initial value of the function from a description of a relationship or from two (x, y) values, including reading these from a table or from a graph. Interpret the rate of change and initial value of a linear function in terms of the situation it models, and in terms of its graph or a table of values.
problem_activity: Task
Complete the table below. Is $\Delta x$ a constant?  If so, what constant is it? What do you notice about the 3rd column of the table?
| $x$ | $f(x)=128\cdot \left({\frac {1}{2}}\right)^x$ |               Successive quotients                |
|-----|-----------------------------------------------|---------------------------------------------------|
|  0  |                      128                      |                       ----                        |
|  1  |                      64                       | $\frac{f(1)}{f(0)}=\frac {64}{128} = \frac{1}{2}$ |
|  2  |                                               |               $\frac{f(2)}{f(1)}=$                |
|  3  |                                               |                                                   |
|  4  |                                               |                                                   |
Complete the table below. Is $\Delta x$ a constant?  If so, what constant is it? What do you notice about the 3rd column of the table?
| $x$ | $f(x)=128\cdot \left({\frac {1}{2}}\right)^x$ |                Successive quotients                 |
|-----|-----------------------------------------------|-----------------------------------------------------|
|  0  |                      128                      |                         ---                         |
|  2  |                      32                       | $\frac{f(2)}{f(0)} = \frac {32}{128} = \frac{1}{4}$ |
|  4  |                                               |                $\frac{f(4)}{f(2)}=$                 |
|  6  |                                               |                                                     |
|  8  |                                               |                                                     |
Let $f(x)=a \cdot b^x$. Let $x_0$ be any particular $x$-value. Show that if $x_0$ is increased by a constant, $\Delta x$, the successive quotient  $$\frac{f(x_0+ \Delta x)}{f(x_0)}$$ is always the same no matter what $x_0$ is.
Is b) an example of the result of c)? Explain.


aligns: no