Mathematica 9 is now available
Student Support Forum
-----
Student Support Forum: 'Matrices & Minors' topicStudent Support Forum > General > Archives > "Matrices & Minors"

Next Comment >Help | Reply To Topic
Author Comment/Response
Kai
07/10/13 3:01pm

Hi all

For exams I am studying matrices and I am using Mathematica for verifying my results. But I have a little trouble here because my minors result matrix looks kinda different.

For example I used this video:
[URL]https://www.khanacademy.org/math/algebra/algebra-matrices/inverting_matrices/v/inverting-3x3-part-1--calculating-matrix-of-minors-and-cofactor-matrix[/URL]

{{-1, -2, 2}, {2, 1, 1}, {3, 4, 5}}

If I look at the minors Mathematica gives this result:
{{3, -5, -4}, {2, -11, -18}, {5, 7, 1}}
where I expect like in the video
{{1, 7, 5}, {-18, -11, 2}, {-4, -5, 3}}

So it is flipped somehow.

But if I take a look at the second video:
[URL]https://www.khanacademy.org/math/algebra/algebra-matrices/inverting_matrices/v/inverting-3x3-part-2--determinant-and-adjugate-of-a-matrix[/URL]

The inverse of the matrix looks all the same both in video and mathematica

{{1/23, 18/23, -(4/23)}, {-(7/23), -(11/23), 5/23}, {5/23, -(2/23), 3/
23}}

Could someone explain this to me? I don't get it :-(

Thanks

URL: ,

Subject (listing for 'Matrices & Minors')
Author Date Posted
Matrices & Minors Kai 07/10/13 3:01pm
Re: Matrices & Minors Peter Pein 07/11/13 2:15pm
Next Comment >Help | Reply To Topic