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for the matrix A=4 -2 9
10 3 9
-6 7 1
a. find the minor of the element 3
b. find the coafactor of the element 7
answer is a. M22= 4 9
-6 1
b. is C32=- 4 9
10 9
I understand a. answer
I do not understand b. answer i do not understand how 10 and 9 is the answer.
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Cofactor
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please help me
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[Moved to Help Me]
The answer is right. The cofactor of an element is exactly the same as its minor, except that it might be multiplied by -1 depending on which element it is.
For an element in the ith row and jth column of the original matrix, its cofactor would be its minor multiplied by (-1)^(i+j). In this case, i+j = 5 and so it would be multiplied by -1.
Why did the vector cross the road?
It wanted to be normal.
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could you please show me step by step b is correct
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Well, you know how to find the minor of the matrix, because you did that for a.
Eliminating the 3rd row and 2nd column of matrix A gives you the minor:
4 9
10 9
Then you need to multiply by -1 to turn that into the cofactor, for the reason I gave in the post above.
Why did the vector cross the road?
It wanted to be normal.
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