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Homework Statement
solve the det
3 1 1 0
-4 5 0 -1
0 7 2 8
2 -1 0 3
Homework Equations
The Attempt at a Solution
I am trying to solve it and get a different answer each time so I am doing something I shouldn't obviously.
Ok I am adding rows to other rows
(ex 2*row1 +row2)
Same I do for columns.
When I expend the matrix I pay attention to the + and -
So what is wrong :S
This is what I did (I didn't choose the shortest way because I wanted to make sure I am solving it right but hence something is off :S)
I did 2*R4+r2,R3-2*R1
I opened the det by a3,1
And got to this by this point:
1*
-4 5 -1
-6 5 8
0 3 5
then I didR1-R2,3*R1+R2
then opened it by a2,1
I got the det:
6*
5 -19
3 5
Which is 492 (should b 82)Now in all the cases I tried I reached 82 before multiplying the number outside the 2x2 det (6 in this case)
Well it is kinda hard showing the steps of the det though it is a simple one but mainly is there something wrong with the steps I take?