Question

If i+j+k and i+aj+3k are two parallle vectors find value of a

Answer 1

Two vectors are parallel if one vector can be written as multiple of other vector.

Let A = i+j+k and B = i+aj+3k ; Here A cannot be written in terms of B by any means (i.e ratio of corresponding x,y and z coordinates is not same ⇒ 1/1 (i components ratio )≠ 1/3  (k components ratio))

So A and B cannot be parallel for any value of a