Tables
First Difference
Example
Write the equation for the function that contains the points in the table below.
Step 1. Make sure the x-values have a constant change.
3 - 2 = 1
2 - 1 = 1, etc.
Yes: 1
Step 2. Find the change from one y-value to the next.
-8-(-2) = -6
-2 - 4 = -6, etc.
Step 3. Use the "first difference" to write a formula.
a = -6
y -intercept, b = (0, 10) as found in the table
Step 4. Substitute values into y = ax + b
y = -6x + 10