Determinants
Inverse of a matrix by using determinants
Essential property: If A is invertible→ |A| ≠ 0
then, since we have A·A-1 = I
Let the cofactor matrix
Then

NOTE: (AdjA)t is called adjoint or adjugate.
Example:

Exercises:
1.- Calculate the inverse of these matrices:

2.- Find the values of k to make A invertible:

Calculate A-1 when k = -5
Solutions:
1)

2) k ≠ -8

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