Math Is Fun Forum

woopypooky2

Guest

simple matrice invert

A = 2 3 -4          M =  1 -10 -7
      1  2  3                -7 10 -11
      3 -1 -1                17 10  1

cof A = 1 10 -7
           7  10  11
           17 10  11
           17 -10 1               

adj A = (Cof A)T and so on.....

Above are some example to get A-¹ from A.

the question is how  to get M from A.
At start, i was only given A, how to get M.

woopypooky2

Guest

Re: simple matrice invert

hello does anyone know?

TheDude

Member

Registered: 2007-10-23

Posts: 361

Re: simple matrice invert

Your cofactor(A) doesn't look correct to me.  I'm not great with matrices, but I think this is the cofactor:

Cofactor(A) = 1  -10  -7
                    -7   10  -11
                    17   10  1
= M

I think this is how you get to M from A.

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woopypooky2

Guest

Re: simple matrice invert

thank you very much dude.

So how do i get cofactor(A) from A?

TheDude

Member

Registered: 2007-10-23

Posts: 361

Re: simple matrice invert

Like I said, I'm not good with matrices, so I had to use this Wikipedia page: http://en.wikipedia.org/wiki/Cofactor_%28linear_algebra%29

Cofactor(A) =

is equal to the determinant of the matrix you get when you eliminate the

row and the

column of A.

For example:

I leave the rest to you.

Last edited by TheDude (2007-10-26 02:15:13)

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woopypooky2

Guest

Re: simple matrice invert

oooo..i got it now, thanks a lot dude. i remember learned it years ago but forgotten already.

TheDude

Member

Registered: 2007-10-23

Posts: 361

Re: simple matrice invert

You'd be amazed at how quickly you can forget even the simple things.

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mikau

Member

Registered: 2005-08-22

Posts: 1,504

Re: simple matrice invert

actually i'd say the simplest things are the easiest to forget. While the hard stuff tends to stick. At least i've observed that with myself.

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A logarithm is just a misspelled algorithm.