# Finding Function Rules

### Use input/output tables or graphs to find function rules

## The first step when using an input/output table is finding the change in y values when the change in x is 1. Typically we want to see our input x values starting at 0 and increasing by 1 each step.

So if we have the following values x y

0 3

1 7

2 11

We can see that as x increases by 1, y increases by 4.

Now that we have this element we want to look at what the y-value is when x is zero.

In our example the y-value is 3

## So our change in y is 4, and our starting point is 3

## Now we need to put these elements together to create our function rule.

## Creating our function

First we need to know what to do with our starting point of 3 and our change in y of 4. The change in y is the coefficient for x, and then we add our starting point. The form that we want our equation to be in is:

y=mx+b

Where m is the change in y, and b is the starting point.

In our example our equation will look like:

y=4x=3

**Now try when the change in y is 8 and the starting point is 27.**

__WATCH THE VIDEO BELOW FOR STEP-BY-STEP INSTRUCTIONS ON HOW TO FIND A FUNCTION USING TWO POINTS IN AN INPUT AND OUTPUT TABLE__

Ex: Find the Linear Function Given Two Function Values in Function Notation