[Math] Proving that a set is linearly independent when vector is not in the Span.

matrices

I understand how to do this when I have values for the vectors, but what if there are no values? I also know that if the solution is trivial, it is independent. Basically, can I solve this with Gauss Jordan elimination when there are no values, and when one vector is not in the span?

Prove that a set {$v_1, v_2, v_3, v_4$} is linearly independent if {$v_2, v_3, v_4$} is
linearly independent and $v_1$ is not in the Span {$v_2, v_3, v_4$).

Best Answer

You cannot use Gauss Jordan elimination, you will have to use the definition of linear independence: A set is linearly independent if it is the case that a linear combination of its vectors equals zero if and only if the coefficients of that linear combination are all zero.

Hint: Any linear combination of $\{v_2, v_3, v_4\}$ can be thought of as a linear combination of $\{v_1, v_2, v_3, v_4\}$ where the coefficient of $v_1$ is zero. For getting that $v_1$ is not in the span, prove this by contradiction, i.e., if $v_1$ is in the span then $\{v_1, v_2, v_3, v_4\}$ is not linearly independent.