Based on the description provided, Table 1 and Table 2 show a symmetry in their outputs (f(x) values) for positive and negative inputs (x), which indicates a quadratic relationship. Quadratic functions are not linear.
Table 3, Table 4, and Table 5 all show consistent or linear changes in their output values as the input (x) increases, indicating that they are linear functions.
Therefore, the tables that do not represent a linear function are:
Table 1 and Table 2.