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Question 978749: Dear tutor,
I have attempted 2 calculating processes for a determinant question, here I say Process 1 and Process 2.
The original question is:
|2 1 1|
|1 -1 1|
|3 -2 3|
Process 1
|2 1 1| | 0 0 1|
|1 -1 1|=|-1 -2 1|=1|-1 -2|=1(5-6)=-1
|3 -2 3| |-3 -5 3| |-3 -5|
Process 2
|2 1 1| |2 1 1| |2 1 1| |3 5 0|
|1 -1 1|=|1 -1 1|=|1 2 0|=|1 2 0|=1|3 5|=1(6-5)=1
|3 -2 3| |5 6 1| |5 6 1| |5 6 1| |1 2|
I have checked with many determinant tools which shown that Process A's answer is correct but Process B's is wrong.
My question is I have checked both Processes(multiplication, addition or substraction)are correct BUT got different answers.
I am very confused what's wrong with Process B which have correct calculating process but got wrong answer.
I hope my tutor can explained DETAILEDLY what's going wrong with calculation in Process B for I will attend Precalculus examination later.
I should show my kindly appreciation in advance.
Answer by Alan3354(69443)   (Show Source):
You can put this solution on YOUR website! The original question is:
|2 1 1|
|1 -1 1|
|3 -2 3|
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That's 3 by 3 matrix, not a question.
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It's not clear what you show that you tried.
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You didn't say what you're trying to do, but you probably want to find the determinant.
Using minors for the 1st row:
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Det = 2*(-3+2) - 1*(3-3) + 1*(-2+3)
= -2 - 0 + 1
= -1
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