Discovering the Properties of a Function

Suppose you would like to use a secret code to hide your cell phone telephone list from your friends. Let the input number be listed at the bottom of the grid. The output numbers are listed along the left hand side. Shade in the red squares to show a matching of the input and output values. Fill in the chart at the bottom of the page to show the connection between the input and output values. Code your telephone number or the cell phone number on the screen INPUT OUTPUT

Use the same coding. Suppose a number has been coded as Use the Coding Chart un-code the coded cell phone number INPUT OUTPUT

Will every cell phone number receive a unique coded cell phone number? Will every coded cell phone number match with exactly one original cell phone number? Can you find a rule that will convert every original cell phone number to a coded cell phone number using the coding chart at the right? Can you find a rule that will convert every coded cell phone number back to its original cell phone number? Output number = 9 - Input Number Input Number = 9 – Output Number

Create a new coding system that can be used to code a cell phone number that is not as systematic as the last coding chart. Step 1: Be sure that the coding system you create will produce a unique coded number. Show your coding chart. Try coding a telephone number by using the one at the right. Step 2: Can you undo the coded telephone number using your chart? What is unique about your coding system that makes it possible to complete step 1 and 2?

Use the chart at the right to decode a telephone number that has been coded Whats the problem with this coding chart?

Try coding a telephone number using this coding: Can you describe the problems you would have with coding a telephone number using this coding system

Can you create a different coding that could be used to create a way to hide your cell phone numbers? What will have to be true with your coding to make it possible to code your telephone numbers and decode your telephone numbers.

For a coding chart to be useful there must be one unique output for each input and one unique input for each output.

What is the function of a coding chart? How does this activity help you understand what a function does?

What is a function? It could be thought of as a Function Machine

Suppose we put some numbers in our Function Machine

Predict what will happen when we put 10 in our Function Machine 3, 4, 5, 6,... 5, 6, 7, 8,

Predict what number must be put in our Function Machine to get an output of 15 3, 4, 5, 6,... 5, 6, 7, 8, ,15,13

What is the Function of this machine? 3, 4, 5, 6,... 5, 6, 7, 8, ,15,13 Add 2

You just discovered the Function of one specific Function Machine

The function of the machine could be described in words and you have to show various inputs and outputs: Cut a number in half 20,12, 8, 4, 3,1, 0

Hold up your Communicators and let me check your output values. Cut a number in half 20,12, 8, 4, 3,1, 0 10,6, 4, 2, 1.5,0.5, 0

You can find the input values given the description of the Function Machine and the output values.

What input values must be put in this Function Machine to obtain the following output values? X 4 20,12, 8, 4,1, 0

Hold up your Communicators so I can check your responses. X 4 20,12, 8, 4,1, 0 5,3, 2, 1,1/4, 0

How does a Function Machine help you understand what a function does in Mathematics?

Collecting data. Find the area of a square given its side

This time place your input and outputs in a table. Find the area of a square given its side

List the output values for the given input values. Find the area of a square given its side

Can you tell me the area of a square whose side is 15? Find the area of a square given its side

Can you tell me what square will have an area of 400? Find the area of a square given its side

A function can be a descriptive relationship.

Place 4 additional number in your chart and in the function. Find the output values. How far is a value from zero?

A function can be a description about a geometric relationship.

Suppose we start with a rectangle that measures 1 by 2. What is its area? Lets dilate the shape by a factor of 2 What is the size of the new rectangle? What is its area? : sq.in. 8 sq.in.

Place 2 input numbers in your chart and in the function. What are the output values? What is the area of a 1 x 2 rectangle if it is dilated by a factor of … : sq.in

Place 2 additional input numbers in your chart and in the function. What are the output values? What is the area of a 1 x 2 rectangle if it is dilated by a factor of … : sq.in

If a dilation causes a 1 x 2 rectangle to increase to an area of 200 what dilation took place? What is the area of a 1 x 2 rectangle if it is dilated by a factor of … 2, 8, 18, , 2, 3, 4, ,

1, 2, 3, 4, 5, 6 2, 2, 2, 2, 2, 2, What is the function of this machine?

1, 2, 3, 4, 5, 6 2, 2, 2, 2, 2, 2, We would say this is not a function because the one input value has many output values.

How does this template help you understand what a function is in mathematics?

Functions can also paint a picture

X 3 2, 3, 4 6, 9, 12 This time we will graph the input and output values. Horizontal Axis: Inputs Vertical Axis: Outputs

X 3 2, 3, 4 6, 9, 12 What patterns do you see? Can you predict other points that will be on the graph?

X 3 2, 3, 4 6, 9, 12 Does the graph paint a picture?

2, 3, 4 4, 4, 4 Horizontal Axis: Inputs Vertical Axis: Outputs Change to 4

2, 3, 4 4, 4, 4 What picture is painted for this function? Write a sentence that describes the output values. Change to 4

How does this template help you understand what a function is in mathematics?