In a solution guide I've read that $\begin{bmatrix}a\\b\\c \end{bmatrix} : a+b+c=2$ isn't a vector space because it doesn't have the zero vector. I'm not 100% sure why this is but I think it's because if you make $a, b, c=0$ you don't get $2$ which is what it's meant to be equal to? Is my thinking correct or not?
Thanks