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Function rules and Other Tight Math Stuff Mr Streety’s 7 th Grade Class

Function rules and Other Tight Math Stuff Mr Streety’s 7 th Grade Class. Writing function rules from tables Writing tables from Function rules Graphing Tables and Function rules Writing Function Rules from Graphs. Function Rules from Tables.

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Function rules and Other Tight Math Stuff Mr Streety’s 7 th Grade Class

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  1. Function rules and Other Tight Math StuffMr Streety’s 7th Grade Class • Writing function rules from tables • Writing tables from Function rules • Graphing Tables and Function rules • Writing Function Rules from Graphs

  2. Function Rules from Tables • There are two ways to write a function rule for a table • The first is through number sense. • This is the Harder of the two

  3. Function rules from tables • When X=0, what does Y=?. • This gives you the first part of your function • y=x+2 • After you find what Y= when X=0, you need to subtract this number from the following values for Y

  4. Apples and Bananas Function Rule • As you know we start with the equation: • y=Ax+B Where A and B are constant numbers, and of course x and y are variables meaning their value changes with the table.

  5. Apples and Bananas • The first step here is to solve for B, using the first set of numbers from the table • y=Ax+B • 2=A(0)+B • B=2 • This gives us the new equation y=Ax+2

  6. Apples and Bananas Function Rule • The second step is to use our new equation to find a value for A • Y=Ax+2 • 5=A(1)+2 • 5-2=A(1)+2-2 • 3=A(1) • A=3

  7. Apples and Bananas Function Rule • Now we have our new equation • y=3x+2 • We can plug our x values in to check the equation • y=3(2)+2 • Y=6+2 • Y=8

  8. Mrs. Robinson's Lawn • We have been hired to mow Mrs. Robinson's lawn. She is going to give us a two dollar bonus for starting early. In addition to this she will pay us 3 dollars an hour. • What is the function rule for this problem?

  9. Writing Tables from Function Rules • Since 2 dollars is a bonus, we get that as soon as we start. We get 3 dollars an hour after that. • Y=3x+2 • First we can choose any values for x we want unless they are given to us.

  10. Tables From Function Rules • The next step is to plug these values in for the variable x in our equation. • Y=3x+2 • Y=3(0)+2 • Y=2

  11. Tables From Function Rules • Now let’s try the next set of numbers. • y=3(1)+2 • y=5

  12. Tables from Function Rules • As you plug in the rest of the values for x, you will get the corresponding values for y.

  13. Graphing Tables and Function Rules • First of all if you only have a function rule you need to make a table which we just covered. • From the table to the left we make a graph

  14. Mrs. Robinson's Lawn • We will need to plot the set of numbers as they as they appear in the table. • For the first set of numbers we will go 0 to the right and up 2 • For the next set of numbers we will go 1 to the right and 5 up

  15. Mrs. Robinson's Lawn • Of course this is just the first two sets of numbers. • Let’s see what happens if we plot the rest of the numbers

  16. Mrs. Robinson's Lawn • After plotting all the points we can draw a line from point to point that will help us find values between the points.

  17. Mrs. Robinson's Lawn • Using the line we can tell how much money we can make mowing her lawn for 2 and a half hours or or four and a half

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