Compute the indicated products
(i) \displaystyle \begin{bmatrix} a & b \\ -b & a \end{bmatrix}\begin{bmatrix} a & -b \\ b & a \end{bmatrix}
(ii) \displaystyle \left[ \begin{matrix} 1 \\ 2 \\ 3 \end{matrix} \right] \left[ \begin{matrix} 2 & 3 & 4 \end{matrix} \right]
(iii) \displaystyle \begin{bmatrix} 1 & -2 \\ 2 & 3 \end{bmatrix}\left[ \begin{matrix} 1 & 2 & 3 \\ 2 & 3 & 1 \end{matrix} \right]
(iv) \displaystyle \left[ \begin{matrix} 2 \\ 3 \\ 4 \end{matrix}\begin{matrix} 3 \\ 4 \\ 5 \end{matrix}\begin{matrix} 4 \\ 5 \\ 6 \end{matrix} \right] \left[ \begin{matrix} 1 \\ 0 \\ 3 \end{matrix}\begin{matrix} -3 \\ 2 \\ 0 \end{matrix}\begin{matrix} 5 \\ 4 \\ 5 \end{matrix} \right]
(v) \displaystyle \left[ \begin{matrix} 2 \\ 3 \\ -1 \end{matrix}\begin{matrix} 1 \\ 2 \\ 1 \end{matrix} \right] \left[ \begin{matrix} 1 & 0 & 1 \\ -1 & 2 & 1 \end{matrix} \right]
(vi) \displaystyle \left[ \begin{matrix} 3 & -1 & 3 \\ -1 & 0 & 2 \end{matrix} \right] \left[ \begin{matrix} 2 \\ 1 \\ 3 \end{matrix}\begin{matrix} -3 \\ 0 \\ 1 \end{matrix} \right]