The proof is below.
Work Step by Step
The proof can be made as follows: 1. Given: A function $mx+b$ where m is not 0. 2. mx+b is a linear equation. 3. If m is not 0, then the line is not horizontal. 4. If the line is not horizontal, then the linear function will pass the horizontal line test. 5. If the linear function passes the horizontal line test, then its inverse is a function.