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Calcmathlete
 2 years ago
Evaluate: \(\left[\begin{matrix}1 & 2 &1 & 3 \\2&3&2&0\\3&1&0&1\\0&0&3&2\end{matrix}\right]\)
Calcmathlete
 2 years ago
Evaluate: \(\left[\begin{matrix}1 & 2 &1 & 3 \\2&3&2&0\\3&1&0&1\\0&0&3&2\end{matrix}\right]\)

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Calcmathlete
 2 years ago
Best ResponseYou've already chosen the best response.0I got 102. Is it correct or did I get an arithmetic error somewhere?

Calcmathlete
 2 years ago
Best ResponseYou've already chosen the best response.0Hmm... Let me just double check everything here...

Calcmathlete
 2 years ago
Best ResponseYou've already chosen the best response.0\[3\left[\begin{matrix}1 & 2 &3\\ 2 & 3 &0\\3&1&1\end{matrix}\right]  2\left[\begin{matrix}1 & 2 &1\\ 2 & 3 &2\\3&1&0\end{matrix}\right]\]Did you end up doing this?

TuringTest
 2 years ago
Best ResponseYou've already chosen the best response.1must be method of cofactors, eh?

asnaseer
 2 years ago
Best ResponseYou've already chosen the best response.2I get 72. But maybe I made a mistake. Might be worth looking at this to help: http://people.richland.edu/james/lecture/m116/matrices/determinant.html

asnaseer
 2 years ago
Best ResponseYou've already chosen the best response.2Look down that web page at the section titled "Larger Order Determinants"

TuringTest
 2 years ago
Best ResponseYou've already chosen the best response.1another source for ya http://tutorial.math.lamar.edu/Classes/LinAlg/MethodOfCofactors.aspx

Calcmathlete
 2 years ago
Best ResponseYou've already chosen the best response.0Well, 72 is one of my answer choices... I did it again, but I got  72? I think it's just an arithmetic error on my part. THanks guys!

asnaseer
 2 years ago
Best ResponseYou've already chosen the best response.2yw :)  crosses fingers in the hope that he did make a mistake :)

Calcmathlete
 2 years ago
Best ResponseYou've already chosen the best response.0Wait, one last thing, when I find the determinants of the 3 x 3, can I just use the diagonal method (I'm not sure of the name) or do I have to use minors?

asnaseer
 2 years ago
Best ResponseYou've already chosen the best response.2as @TuringTest said, use the method of cofactors  see the links we gave you.

Calcmathlete
 2 years ago
Best ResponseYou've already chosen the best response.0Ok, once again, thank you :)

TuringTest
 2 years ago
Best ResponseYou've already chosen the best response.1the problem in what you did is that you forgot that all elements on the diagonals will give positive minors.

TuringTest
 2 years ago
Best ResponseYou've already chosen the best response.1I phrased that poorly, not sure how to say it without giving away the answer

asnaseer
 2 years ago
Best ResponseYou've already chosen the best response.2Also, determinants are usually written with straight lines on either side of the matrix elements  instead of the square brackets that you used.

Calcmathlete
 2 years ago
Best ResponseYou've already chosen the best response.0Oh! I got it! And @asnaseer for some reason, I see them written both ways when doing school work?

asnaseer
 2 years ago
Best ResponseYou've already chosen the best response.2Hmmm  ok, well I was taught that straight lines is what should be used. Maybe the notation differs from country to country?

TuringTest
 2 years ago
Best ResponseYou've already chosen the best response.1if it's left in brackets it should at least say \(\det\) in front of it In the US we use what @asnaseer said

asnaseer
 2 years ago
Best ResponseYou've already chosen the best response.2Here is an example of how we are taught in the UK: http://www.intmath.com/matricesdeterminants/matrixdeterminantintro.php

asnaseer
 2 years ago
Best ResponseYou've already chosen the best response.2Also, when working with algebra, if you have a matrix A, then we would write its determinant as either:\[A\]or:\[det(A)\]
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