If AX = I (identity matrix), We can get the value of X if we do this operation (1/A)

which sentence is true

if A is a n x n matrix, then the reduced row echelon form of A is I (identity matrix)

if A is a n x n matrix, then the equation AX = b has exactly one solution for every n x 1 vector b

if A is a n x n matrix, then the equation AX = 0 has exactly one solution.

If A is invertible, then AX = b has exactly one solution, namely A^-1 b

If A is not invertible, then AX = b has no solution

If A is n x n invertible matrix, then KA is invertible for any nonzero scalar n; (KA)^-1 = (1/k)A^-1

if a product AB is not invertible, then A or B is not invertible.

if A or B are invertible, then AB can be invertible in one case

det(A) = …. A is a 2x2 matrix

A^-1 = 1/det(A) [d -b -c a]

det(A) =

det(A), A is a

if A is a square matrix, then the minor of entry aij is denoted by Mij and is defined to be determinant of the submatrix that remains after the ith row, and the jth column are deleted from A

The number (-1)^i+j Mij is denoted by Cij and is called the cofactor of entry aij

if A is an n x n matrix, then the number obtained by multiplying the entries in any row or column of A by corresponding cofactors and adding the resulting products is called the determinant of A, the sums themselves are called cofactor expansions of A

the best strategy for cofactor expansion is to expand along a row or a column with the most zeros

if A is an nxn triangular matrix (upper triangle matrix, lower triangle matrix, diagonal) then det(A) is the product of the entries on the main diagonal of the matrix