Here, \[P+Q=P-Q\] \[P+Q-P+Q=0\] \[2Q=0\] \[\therefore Q=0\] Thus, the vectors $(P+Q)$ and $(P-Q)$ will be equal if $Q$ is a null vector.

Show that two vectors of different magnitudes cannot be combined to give zero resultant, whereas three vectors can be.

If a vector B is added to A, under what condition does the resultant vector have a magnitude equal to A+B?