Write a function rule, in slope-intercept form, that models this situation:

The table shows the amount of pet food in cups remaining in an automatic feeder as a function of the number of meals the feeder has dispensed.

number of meals dispensed (x)
1
3
5
7

amount of pet food remaining (y)
25
17
9
1

1 answer

To find the function rule in slope-intercept form (\(y = mx + b\)), we first need to determine the slope (\(m\)) and the y-intercept (\(b\)) using the data provided:

The meals dispensed (x) and the corresponding amount of pet food remaining (y) are as follows:

\[ \begin{align*} 1 & : 25 \ 3 & : 17 \ 5 & : 9 \ 7 & : 1 \ \end{align*} \]

Step 1: Calculate the Slope (m)

We can use two points to calculate the slope. Let's use the points (1, 25) and (3, 17).

The slope \(m\) is given by the formula:

\[ m = \frac{y_2 - y_1}{x_2 - x_1} \]

Using the points (1, 25) and (3, 17):

\[ m = \frac{17 - 25}{3 - 1} = \frac{-8}{2} = -4 \]

Step 2: Find the Y-Intercept (b)

We now use one of the points along with the slope to find the y-intercept \(b\). We'll use the point (1, 25).

The equation in slope-intercept form is:

\[ y = mx + b \]

Substituting \(m = -4\) and the coordinates of the point (1, 25):

\[ 25 = -4(1) + b \]

Solving for \(b\):

\[ 25 = -4 + b \ b = 25 + 4 \ b = 29 \]

Step 3: Write the Function Rule

Now that we have both \(m\) and \(b\), we can write the equation:

\[ y = -4x + 29 \]

Conclusion

The function rule in slope-intercept form that models the situation is:

\[ y = -4x + 29 \]