Determinants

A determinant is the resulting number if we operate in a square matrix in a specific way:

•Order 1:

 
•Order 2:

Examples:
 
 
•Order 3: Sarrus’s rule
   
 
 
Example:
 
•Order n (n > 3): The minor of the element aij, αij, is the determinant of the resulting matrix when we remove its file and column. The cofactor of the element aij is:
 Aij = (-1)i+j·αij
 
Example:
 
Then:
Example:
 
 
Exercise: calculate:
 
 
 
 
 
 
Solutions: a) 9; b) -15; c) 6

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