standard_description: 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.)
problem_activity: Activity
This practice activity is similar to the last activity in the associated Algebra 1 lesson, except that students are asked to find specific information about the contexts before being asked to compare them.
To give students a greater opportunity to communicate their thinking verbally and listen to the reasoning of others, we recommend assigning each student to either work on function
\(m\)
or
\(p\)
for the first question, and then get together in groups of 2–4 to tackle the remaining questions.
Launch
Arrange students in groups of 2. In each group, one partner completes the first question for function
\(m\)
, and the other partner for function
\(p\)
. Then, partners should work together using the information they found in the first question to complete the remaining questions.
It’s a judgment call about whether to ask students to find the maximum of function
\(m\)
without a graphing calculator or provide access to graphing calculators. In the associated Algebra 1 lessons, there are times when students are asked to answer such a question without graphing.
Student Facing
Two objects are thrown into the air. The height of object M in meters is modeled by the function
\(m(x)=(5+10x)(1.5-x)\)
with
\(x\)
representing time in seconds. The height of object P in meters is modeled by the function
\(p\)
, represented by the graph.
[IMG]
For each object, determine:
the time at which the object hit the ground
the height from which the object was thrown
the maximum height of the object
the time at which the object reached its maximum height
Which object was launched from a greater height? Explain your reasoning.
Which object hit the ground first? Explain your reasoning.
Which object reached a greater maximum height? Explain your reasoning.
Student Response
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Activity Synthesis
Much of the conversation will take place within groups. Time permitting, invite students to create a visual display of their solutions and explanations. Give students an opportunity to review other groups’ work, and time to revise and refine their own work. If desired, select a few exemplary visual displays to keep posted in the classroom to support students in later lessons.


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