Chapter 4 - Exponential and Logarithmic Functions - Section 4.2 One-to-One Functions; Inverse Functions - 4.2 Assess Your Understanding - Page 290: 12

The function is a one-to-one function.

For each value of $x$, there must be a unique $y$ value paired with it and every element of the domain (D) must be paired with a unique element of the range (R). Therefore, the function is a one-to-one function.