A family of nontrivial coefficients proves that the associated vectors are linearly dependent. Specifically, if a parametric solution to the homogeneous equation allows choosing a nonzero parameter (such as in coefficients like ), the resulting linear combination equals the zero vector with at least one nonzero coefficient, satisfying the definition of dependence.
Conditions: You have a specific set of vectors.; You have found a parametric family of solutions to the homogeneous equation.; The parameter can be chosen to be nonzero.