# Simple Vector Problem. Help please!

Hey everyone,
I know this problem is easy but im having some trouble. If someone could point me in the right direction i would be really grateful.
Suppose (vector)C=(vector)A + (vector)B
a) under what circumstances does [A]=+[C]?
b) Could [C]=[A]-?
( [ ]= absolute value)
Ok. For A i think that A and B would have to have the same signs but Im really not to sure.
For B i cant see how C=A+B can be equal to [C]=[A]-. It seems like a simple contradiction, which usually means im wrong. :tongue2:
I would really apprecitate some help!!!!