select all of the following tables which represent y as a function of x.

Explanation:

Step1: Recall function definition

A relation is a function if for each input $x$ there is exactly one output $y$.

Step2: Check first table

In the first table, when $x = 3$, $y$ has two values ($1$ and $16$), so it is not a function.

Step3: Check second table

For each $x$-value in the second table, there is a unique $y$-value. So it is a function.

Step4: Check third table

Each $x$-value in the third table has a single corresponding $y$-value. So it is a function.

Step5: Check fourth table

When $x = 1$, $y$ has two values ($3$ and $6$), so it is not a function.

Answer:

The second and third tables represent $y$ as a function of $x$.