options: Understand that a function is a rule that assigns to each input exactly one output. The graph of a function is the set of ordered pairs consisting of an input and the corresponding output. (Function notation is not required in Grade 8.)

Interpret the equation y = mx + b as defining a linear function, whose graph is a straight line; give examples of functions that are not linear. For example, the function A = s2 giving the area of a square as a function of its side length is not linear because its graph contains the points (1,1), (2,4) and (3,9), which are not on a straight line.

Compare properties of two functions each represented in a different way (algebraically, graphically, numerically in tables, or by verbal descriptions). For example, given a linear function represented by a table of values and a linear function represented by an algebraic expression, determine which function has the greater rate of change.
problem_activity: Problem 1
Determine the rate of change in each situation. Then describe the relationship using function language (for example, ____ is a function of ____ because _____.)
a.
|  Amt of watermelon in pounds,                                 $$x$$  |   |   |   |   |   |   |
|----------------------------------------------------------------------|---|---|---|---|---|---|
| Cost of watermelon in dollars,                                 $$y$$ |   |   |   |   |   |   |
b.
$${d=25t}$$
, where
$$d$$
is distance in miles and
$$t$$
is time in hours
c.    Giovanni can decorate
$$2$$
cakes,
$$c$$
, every
$$5$$
hours,
$$h$$
.
Problem 2
Determine the starting or initial output value in each situation.
a.
| **                Distance traveled in cab in miles,                *                   $$x$$                  * ** |  0   |  1   |  3   |   4   |
|---------------------------------------------------------------------------------------------------------------------|------|------|------|-------|
|    **                Cost of cab ride in dollars,                *                   $$y$$                  * **    | 2.50 | 4.75 | 9.25 | 11.50 |
b.
| **                Distance traveled in cab in miles,                *                   $$x$$                  * ** |  1   |  2   |   4   |   5   |
|---------------------------------------------------------------------------------------------------------------------|------|------|-------|-------|
|    **                Cost of cab ride in dollars,                *                   $$y$$                  * **    | 4.50 | 7.00 | 12.00 | 14.50 |
c.
$${p=16d+20}$$
where
$$p$$
is the total number of pages read in a book and
$$d$$
is the number of days
Problem 3
The function formula below shows the relationship between temperature in degrees Fahrenheit and degrees Celsius. °F is a function of °C.
$${F=\frac{9}{5}C+32}$$
a.   Determine what 28°C is in °F.
b.   Determine what 23°F is in °C.


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