Using this, we can think of the table as telling us this:
Now as for making a function. What can we decide from the table? It looks like if x =0, f(x)=f(0)=1. So it looks like we need to have a constant that isn't multiplied by any x.
Next, lets looks at the values, how can we turn 2 into 7 and 4 into 13?
Looks like . Does this make sense how we came to this? It can be a bit of a trial and error process.
Let's test it.
Can you find now?