SOLUTION: Please help me solve this eqaution: give the determinant 5, 4, 2, 1, 7, 3, 4, -1, 1 (write the minor of element 3 and write down co-factor of element 3.

Algebra ->  Matrices-and-determiminant -> SOLUTION: Please help me solve this eqaution: give the determinant 5, 4, 2, 1, 7, 3, 4, -1, 1 (write the minor of element 3 and write down co-factor of element 3.      Log On


   

Question 962323: Please help me solve this eqaution: give the determinant 5, 4, 2, 1, 7, 3, 4, -1, 1 (write the minor of element 3 and write down co-factor of element 3.
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!
give the determinant matrix%283%2C3%2C5%2C+4%2C+2%2C+1%2C+7%2C+3%2C+4%2C+-1%2C+1%29 (write the minor of element 3 and write down co-factor of element 3.
The minor of the 3 in the row 2 is the 2%2A2 determinant which contains only the elements of determinant that are NOT in the same row or the same column (which is column 3) as that 3.


matrix%283%2C3%2C5%2C+4%2C+2%2C+1%2C+7%2C+3%2C+4%2C+-1%2C+1%29


The minor of that 3 is this determinant:

matrix%282%2C2%2C5%2C+5%2C+4%2C+-1%29 = 5%28-1%29+-+4%285%29+=+-5+-20+=+-25

As you can see, the minor for row 2 and column 3 is M23+=+-25.

The cofactor is -1 times minor -25;so, it is 25