The velocity of the source is positive if the source is note that this equation may not use the sign convention you are accustomed to. think about the physical situation before answering.

a. traveling in the +x direction
b. traveling toward the listener
c. traveling away from the listener

Answer is "B"

Explanation:

A physical situation of this question can be conceived as follows: If a siren is blowing through a certain distance in motion, then the listener find out that the velocity of the sound wave increases as the source of the siren is approaching the listener. The listener hear the maximum sound frequency and velocity of the source as it reaches him. However, the source velocity decreases as the siten moves away from the listener which can be said to be negative. Therefore, the correct answer is that the velocity increases as the source is moving towards the listener which is option "B"

i. like it i'm gonna edit it tomorrow

it is a negative acceleration