Finding the Adjoint of a Matrix

[geffman1]

hey guys, just need a little help. say your got a matrix
1 2
3 4

how do you find the adjoint, i can get the right numbers but i can't work out y the signs change. any help would be helpful. thanks guys.

 

[Dick]

The adjoint is just the transpose, isn't it? Or are you talking about the adjugate? They are different.

 

[geffman1]

i think its the transpose of the cofactor matrix
but i don't know how to get the cofactor matrix?? thanks

 

[Dick]

That's actually the adjugate not the adjoint. Try the wikipedia entry http://en.wikipedia.org/wiki/Adjugate It's pretty good and not that hard. You can also look up cofactor matrix from the same source. Also nothing wrong with the entry. You can save me a lot of writing that way.