You can find the average difference between rows. For example, in the first one, between the ys, it changes by 1, then 3, then 5, then 7. If you look at the changes between these you get 2 each time. Because you had to look at the differences twice, its quadratic. It's linear if you had to look at it once. Exponential you can just see if you can multiply the same constant between each row.
