Final answer:
To determine which of the given functions has an inverse that is not a function, we need to determine if each function is one-to-one.
Step-by-step explanation:
In order for a function to have an inverse, it must be a one-to-one function. A one-to-one function means that each unique input value maps to a unique output value. Looking at the given functions:
- y = 2x + 1: This is a linear function, and it is a one-to-one function. So, it has an inverse that is a function.
- y = x²: This is a quadratic function, and it is not a one-to-one function because multiple input values can have the same output value. So, it does not have an inverse that is a function.
- y = x: This is a linear function, and it is a one-to-one function. So, it has an inverse that is a function.
Therefore, the function y = x² has an inverse that is not a function.