基本的线性代数。
两个行列数相同的矩阵才能加减。
Matrix x Vector -> Vector
m x n n x 1 m-dimensional vector
Properties:
1.矩阵乘法 A X B != B X A
2.矩阵乘法满足 A x B x C = A x (B x C) = (A x B) x C
但是a b c 的排列顺序不能换!
3.Identity Matrix : n x n且 只有左对角不为0
A x I = I x A = A 当 I 为 Identity Matrix
4.Inverse
if A is an m x m matrix, and if it has an inverse,
A x A(-1) = A(-1) x A = I
5.Transfer
B = Transfer A
-> Bi,j = Aj,i