MIT线性代数笔记-第三讲

Rules for matrix operations
A * B = C
1.regular way
The entry in row i and column j of AB is (row i of A) dot product(column j of B)

2.column way
every column of c is combination of the columns of A

3.each row of c is combination of the rows of B

4.block way

inverse

calculating A−$A^{-}$ by Gauss-Jordan(solve 2 equations at once)

步骤的关键是利用E[AI] = [IA−$A^{-}$]
也就是有一个进行elimination的转换矩阵E，E * A = I，那么I * E必定为A的逆