Question

Mel works as a delivery person for Amazon. The graph shows a linear model for his delivery times on

different days.
(a) What is the equation of the line, first written in point-slope form and then written in slope-intercept
form? Show how you determined the equation.
(b) Based on the linear model, predict how long it initially took Phillip to deliver his packages.
Approximately how much did his delivery time decrease per day?

Answer 1

Point slope form: -9 = m(3)

Slope intercept form: y = -3x + 30

At x = 0, his delivery time was 30 minutes. It decreased by 3 minutes per day.

Explanation:

We have 2 points to calculate the line.

(3, 21) x1 y1

(6, 12) x2 y2

First, we need to calculate the slope.

m =

m =

m = -3

Point slope form is:

y - y1 = m(x - x1)

So for our case:

-9 = m(3)

And slope intercept form is:

y = mx + b

We need to solve for the y intercept (b)

y = -3x + b --- enter the slope

21 = -3(3) + b --- enter in any point on the line for x and y

21 = -9 + b

b = 30 --- solve for b

Now our slope intercept form of the line is:

y = -3x + 30

At x = 0, his delivery time was 30 minutes. It decreased by 3 minutes per day.