A set of ordered pairs represents a function if each input (x-value) is associated with exactly one output (y-value). In other words, no x-value should be repeated with different y-values.

Let's examine each set of ordered pairs:

1. $\{(-2,3), (2,-9), (9,-7), (-2,9)\}$

   • The x-value $-2$ is repeated with different y-values (3 and 9).
   • This set does not represent a function.

2. $\{(-9,8), (5,8), (-8,2), (-1,6)\}$

   • All x-values are unique.
   • This set represents a function.

3. $\{(-3,-4), (-8,2), (-5,-6), (6,2)\}$

   • All x-values are unique.
   • This set represents a function.

4. $\{(4,8), (-7,-8), (-8,-8), (-1,-5)\}$

   • All x-values are unique.
   • This set represents a function.

Therefore, the set of ordered pairs that does not represent a function is:

$\{(-2,3), (2,-9), (9,-7), (-2,9)\}$

Would you like more details or have any questions? Here are five related questions for further exploration:

1. What is the definition of a function in mathematics?
2. How can you determine if a graph represents a function?
3. What is the vertical line test and how is it used?
4. Can a function have the same y-value for different x-values?
5. How do you find the domain and range of a function?

Tip: When checking if a set of ordered pairs represents a function, look for repeated x-values with different y-values. If you find any, it is not a function.