2.4 Rules for Matrix Operations – 矩阵运算规则
一个矩阵如果有m行n列,那它就是一个m×nm\times nm×n矩阵
当两个矩阵形状相同的时候,就能够被相加。矩阵也能够被任意常数c所乘
[123400]+[224499]=[347899] and 2[123400]=[246800]
\left[\begin{array}{ll}
{1} & {2} \\
{3} & {4} \\
{0} & {0}
\end{array}\right]+\left[\begin{array}{ll}
{2} & {2} \\
{4} & {4} \\
{9} & {9}