FUNctions!!By: Baylee McBride

Real-World Problem

Sally is trying to figure out how much her bill cost for texting each month for 6 months. She sent 102, 105, 122, 127, 139, and 155 text messages. If text messages cost 10 cents per text how much money did it cost each month?

The Equation

The equation to my problem is ….

x(.10)=y or f(x)= x(.10)

(function notation)

X= text messages (independent)Y= bill (dependent)

Independent and Dependent

The independent variable is my x value which is the number of text messages sent.

The dependent variable is my y value which is the cost of the bill per month.

We know that y DEPENDS on x.So the total cost of her bill per

month DEPENDS on the number of text messages she sends per month.

90 1001101201301401501600

5

10

15

20

Series1

number of textscost

of

bill

X axis

Y axis

dependent

I n d e p e n d e n t

Table of Values

X X(.10) Y X,Y102 102(.10) 10.20 102,10.20

105 105(.10) 10.50 105,10.50

122 122(.10) 12.20 122,12.20

127 127(.10) 12.70 127,12.70

139 139(.10) 13.90 139,13.90

155 155(.10) 15.50 155,15.50

Domain and Range

Domain is the x values. (input)Range is the y values. (output)

So my domain is {102, 105, 122, 127, 139, 155}

My range is {10.20, 10.50, 12.20, 12.70, 13.90, 15.50}

Domain- X>O Range- Y>O

Continuous or Discrete????

Since my data contains only points and not a line, then it is a discrete graph.

You can not send 100 ½ texts, you can only send 101, 102, or 103 texts. So we will not use any of the numbers between 101 and 102.

Is it a Function?

A function is where each x value has a unique y value.

This means that the x values CAN NOT repeat.

Since my X values do not repeat, then it IS a FUNCTION.

Text Messaging Graph

90 100 110 120 130 140 150 1600

2

4

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8

10

12

14

16

18 Messaging Bill

Seri...

number of texts

cost

of

bill

Y axis

X axis

SOOO……………………………

So the totals for the months were ……..

1st month- $10.20 2nd month- $10.50 3rd month- $12.20 4th month- $12.70 5th month- $13.90 6th month- $15.50