Yes, $y=2x+1$ is a function.
Work Step by Step
The relation $y=2x+1$ will be a function if each x-value corresponds to just one y-value. For each x-value that we plug into the equation, the addition and multiplication performed give us a single value for y, so only one y-value will be associated with each x-value. Therefore, $y=2x+1$ must be a function.