Observe the graph :

Select the points from the graph and place them in a table.

Table :

Find the difference between the -values and diffrence between -values:

and 

and 

and 

Therefore, the difference between the –values is , while the difference between the –values is .

Hence the equation is . 

Check the solution by substituting -values in the function :

When , .

When , .

When , .

When , .

Therefore, the -values are satisfied the equation.

So the function is .

The function is .