# What is the matrix product $$\begin{bmatrix} a \\ 2a \\ 3a \end{bmatrix} \begin{bmatrix} 1 & 0 & -1 \end{bmatrix}$$

What is the matrix product $$\begin{bmatrix} a \\ 2a \\ 3a \end{bmatrix} \begin{bmatrix} 1 & 0 & -1 \end{bmatrix}$$ ?

1. $$\begin{bmatrix} a & 0 & -a \\ 2a & 0 & -2a \\ 3a & 0 & -3a \end{bmatrix}$$
2. $$\begin{bmatrix} a & 2a & 3a \\ 0 & 0 & 0 \\ -a & -2a & -3a \end{bmatrix}$$
3. $$\begin{bmatrix} 2a & 0 & -2a \end{bmatrix}$$
4. $$\begin{bmatrix} 6a & 0 & -6a \end{bmatrix}$$
5. $$\begin{bmatrix} 0 \end{bmatrix}$$