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# Matrices help plz! watch

1. Hi, was wondering if anyone can help me with the following questions. I've been wrking on them for ages but i cant seem to get them to correspond to the answer given on my solution sheet. Working and help appreciated, thanks!

The first question is to find the determinant of the matrix.

Second and third question is to show that the matrix reduces to the one on the right...but I cant seem to get the same answer. Can anyone show me the right steps? Thanks very much!
2. The 1st one, just do like normal
Det(A) = ∑(-1)i+1 a1i . Det(Ai )
where Ai is the matrix formed from A delete the 1st row and the ith column.
3. 1) det = 13
4. Thanks for the help!
5. (Original post by rockiee)
So far I've got:

My Solution so far
det = -2(2(4(1)-2(-2)) - (3(1)-(-1)(-2)) + 2(3(2)-4(-1))) + 3(-(3(2)-2(-2)) - (2(2)-(-1)(-2)) - (2(2)-3(-1)))
..... = -2(2(8) - (1) + 2(10)) + 3(-10 - (2) - (7)) = 2(35) + 3(-19)
...... det = 13

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Updated: November 25, 2005
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