Explanation:
For a quadratic equation, the second differences will always be the same.
First, we must calculate the first differences between the output, or the y values. This can be calculated as shown, taking the first value and subtracting the second value from that (e.g. 34 - 17 = 17, and 1-2 = -1):
34 17 6 1 2 9 22
\ / \ / \ / \ / \ / \ /
17 11 5 -1 -7 -13
The second differences are the differences between the differences we just calculated. This can be calculated as shown:
17 11 5 -1 -7 - 13
\ / \ / \ / \ / \ /
6 6 6 6 6
The second differences are all 6, and as a result, we can verify that this is a quadratic relation