Graphs
Writing a Function
Example 3
Write an exponential function 
for a graph that includes (2, 4) and (3, 16).
for a graph that includes (2, 4) and (3, 16). Step 1. Since the two points have an x-increment of 1, the ratio between their y-values is the common ratio. Use this to find the value of b.
Step 2. Substitute either point into , solve for "a."
Using (2,4) 
Using (3,16) 
Step 3. Substitute "a" and "b" into the original function .
