Final answer:
The designation of the backward direction as negative(-) and the change in velocity as positive(+) means that acceleration is to the left. This is reasonable because the object initially has a positive velocity and a negative acceleration opposes the motion. This acceleration is called deceleration as it has a direction opposite to the velocity.
Step-by-step explanation:
The minus sign indicates that acceleration is to the left. The designation of the backward direction as negative(-) and the change in velocity as positive(+) means that acceleration is to the left. This is reasonable because the object initially has a positive velocity and a negative acceleration opposes the motion. This acceleration is called deceleration as it has a direction opposite to the velocity.
This sign is reasonable because the object initially has a positive velocity in this problem, and a negative acceleration would oppose the motion. Again, acceleration is in the same direction as the change in velocity, which is negative here. This acceleration can be called a deceleration because it has a direction opposite to the velocity.