• Brainly User
If only the Table of values are given, and the function/equation is not explicitly stated:

1) Find the difference between two consecutive values in output or range (y).  The result is called the first difference, and they vary.

2)  Find the difference between two consecutive values in the first difference results.

If the results in the second difference are uniform, then the table of values represents a quadratic function.

(Click the image below for the example.)