If -->B is added to -->A , under what conditions does the resultant vector have a magnitude equal to A + B? Under what conditions is the resultant vector equal to zero?

See explanation below

Explanation:

For two vectors A and B to have a positive resultant, they must both move in the positive direction i.e along the positive x axis

For two vectors A and B to have a zero resultant, they must both have the same magnitude but move in the opposite direction i.e one in the positive direction while the other in the negative direction.

Fie example if A = +5N, B = -5B

So that A+B = +5-5 = 0N

good looking response

newton's first law of motion