Let u and v be distinct vectors in a vector space V show that {u,v} is linearly dependant if and only if u or v is a multiple of the other.
Thanks in advance.
A set of vectors are linearly dependent if vectors satisfy where a_i is a scalar and the set of scalars are not all 0.
So applying this to your problem, you have two vectors. Assume that they are linearly dependent then apply the definition and you can easily show u or v is a multiple of the other. Then assume one is a multiple of the other and show that when this is true the two vectors satisfy the definition of lin. dep.