Reflection: Real World Applications What is a Function? - Section 2: Introduction + Guided Practice


Multiple examples: Today's topic can feel very abstract for some students, especially for those who have never been introduced to the idea of a "function" in math. The more real world examples I am able to use in my explanantion of a function, the better students are able to conceptualize what is going on.

I stray far away from the explanation "it's not a function if the first number repeats". This brief "shortcut" allows students to answer numerical questions, but fails to help them understand the significance of functions in mathematics. It also hinders their success for future lessons that need students to think critically about domain, range, and algebraic relationships.

Additional examples that I have used to describe a function:

-number of cats vs. number of legs --> which relation is the most resonable? {(1,4) (2,8) (2,8) (3,12)} or {(1,4) (2,8) (2,9) (3,12)} Which relation is a function and why? Are you able to predict the output for each input? 

-day of the week vs. temperature

-y = x + 3. when x is 4 the output is usually 6, but sometimes the output is 7. Is this a reliable situation? Will you always know what the output will be when "4" is inputted?

-Draw two "function machines" on the board: Examples

  Multiple Examples
  Real World Applications: Multiple Examples
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What is a Function?

Unit 2: Linear & Absolute Value Functions
Lesson 1 of 10

Objective: SWBAT identify functions from ordered pairs, a table, a graph, and a mapping diagram.

Big Idea: Students will identify whether a relation is a function by examining its inputs and outputs or with the vertical line test.

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