# Math Help - matrix vectors

1. ## matrix vectors

2. Originally Posted by 00hyvs45
1) First multiply the matrix out and get the conditions a+2b-c = 0. Then try to prove both closure under addition and closure under multiplication.

2)Both fail.
i) $\displaystyle A = \left[ \begin{array}{cc} 1 & 0 \\
0 & 1
\end{array} \right]$
and $B = -A$

ii) $\forall A \in S$, $\lambda = 0 \Rightarrow \lambda A = 0 \notin S$