x | y | 1st difference | 2nd difference
-10 | 200 | |
-9 | 162 | 162-200 = -38 |
-8 | 128 | 128 - 162 = -34 | -34 - (-38) = 4
-7 | 98 | 98 - 128 = -30 | -30 - (-34) = 4
-6 | 72 | 72 - 98 = -26 | -26 - (-30) = 4
Since the first differences all are different, then the function is not linear.
Given that all the second differences are equal, then the function is quadratic.
