what is the function when your numbers are 1=40, 2=68, 3=116

This isn't linear.....let's see if it could be a quadratic in the form of ax^2 + bx + c

We have the following system of equations

a + b + c = 40     (1)

4a + 2b +  c  = 68   (2)

9a + 3b + c = 116    (3)

Subtracting (1) from (2)  gives us      3a + b  = 28      (4)

Subtracting (2) from (3)  gives us      5a + b  = 48       (5)

Subtracting (4) from (5)  gives us  2a = 20   ...so..   a = 10    

And substituting this into (4) gives us that b = -2     

And substituting these two values into (1) we have that c = 32

So our function is

f(x)  = 10x^2  - 2x + 32

Here's the graph with a table of values......everything checks out........https://www.desmos.com/calculator/kpamboet7h