4.3 Finding Quadratic Models
Steps to Finding Quadratic Models:
1.
2.
3.
4.
Define the variables and adjust the data (if needed).
Create a scatterplot.
Select a model type (linear or quadratic).
Under the STAT CALC menu, select either 4: LinReg (ax + b) or 5: QuadReg as determined in
step three. Be sure to tell your calculator to calculate it after making your selection.
Example: The total revenue from selling cycling gloves is given in the table.
Price ($)
Revenue ($)
10
400
15
473
20
500
25
476
30
405
a. Find an equation for a model of these data.
b. Graph your model and determine the vertex using the CALC button on the top row of your
graphing calculator. Explain the meaning of this vertex for your model.
c. What does your model predict the revenue will be if the gloves sell for $22 a piece?
d. Give a reasonable domain and range for your model.
Example: Of the total number of people who own a home computer, the percentage of those who use
their home computers six or seven days a week varies by age. Some of these percentages are given in
the table.
Age
25
35
45
55
65
Percentage
26.7
24.2
24.3
26.6
29.7
a. Find an equation of a model of these data.
b. Give a reasonable domain and range for this model.
c. Estimate the percent of 15-year-olds who use their home computers six or seven days a
week.
Homework: None