Plus and minus signs are used in one-dimensional motion to indicate direction. what is the sign of an acceleration that reduces the magnitude of a negative velocity? of a positive velocity?

Positive sign for negative velocity and minus sing for positive velocity

Explanation:

In the case of the negative velocity, the sign of the acceleration that reduces its magnitude is the positive sign, since being in the opposite direction  to the movement indicates a deceleration or braking. In the case of the positive velocity, the sign of the acceleration that reduces its magnitude is the negative sign, since being in the  opposite direction to the movement indicates a deceleration or braking. We observe that there will always be a reduction in the magnitude of the velocity if the acceleration goes in the opposite direction.

no sign of dia of fuel cell