Equivalent quadratic expressions
Immunization against the common cold

A research lab is trying to develop an immunization against the common cold. Recent tests on a newly-developed substance have showed that taken in small doses it reduces the chances of catching a cold. However, taken in large doses not only doesn't help but actually increases the chance of catching a cold.

During the study, different doses were given in the form of a pill to seven groups of people. Each group consisted of several hundred people. Subjects were tracked for 4 months during the winter. A quadratic function describes the dependence on dosage (in miligrams) of the percentage of people that did not catch a cold.


percentage of people who did not catch a cold
dosage in miligarms


The following questions are important to researchers:
  • What are the chances (in percentages) of a person catching a cold during the winter without the immunization?
  • What is the recommended dosage for minimizing the chances of catching a cold?
  • Is there a dosage so large that it would cause a person to catch a cold for certain? If so, what is it?
  • At what dosage would the substance have no effect, so that the chances of catching a cold would be the same as for those who were not immunized?



    Use correspondence rules to present your answers

    Construct a correpondence rule that describes the dependence of the chance of catching a cold on the dosage. Display a graph and a value table.
  • Answer the questions asked by the researchers. Explain how you can find the answers using one or more of the function's representations (graph, value table, or correspondence rule).
  • Suggest other correspondence rules for the same function. Sugget a correspondence rule for each research question that enables you to glean the answer to the question easily.








  • Vertex Form
    Polynomial Form
    Product Form

    Reading information about functions
    Immunization against the common cold
    Numeric surprises
    Constructing functions
    Wage increase
    Partial pictures
    Examining value tables
    Families of functions
    Vertex paths
    Family and sub-families
    Parametric families

    Exercise 1
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    Exercise 7
    Exercise 8
    Exercise 9
    Exercise 10
    Exercise 11
    Exercise 12