Matrices

Question 1

Commute Matrices

Answer 1

If a matrix is commute it means that AB = BA

Question 2

Finding inverse of a matrix (2x2)

Answer 2

1) Find det.
2) Do 1/det
3) Switch numbers diagonally and put 4) Negatives on other diagonal line

Then to find inverse matrix do: 1/det (matrix you just built with flipping and negatives (steps 3,4)

Question 3

Finding Inverse of (3x3)

Answer 3

1) Find Det.
2) Matrix of Cofactors and also do +/- shit. Find determinant of the cofactors (small 2x2 grids all 9 of them produce 1 determinant which then makes a matrix)
3) Transpose that matrix
4) Multiply by 1/Det.

That gives you the inverse, recall that A * A inverse is = I (identity matrix)

Question 4

What if det = 0

Answer 4

Then inverse of that matrix is non existant