1. The problem statement, all variables and given/known data The question states "let u= 2i+mj-10k and v=i-3j+nk, find the value of n and m such that u,v are parallel", the second part states asks the same but "u,v are perpendicular" 2. Relevant equations 3. The attempt at a solution I attempted to use a dot product solution I guess, because vectors u+v should equal 0 when perpendicular. I'm lost on what to actually do. Thanks in advance.