   FP3 Matrices!!! HELP
  Hiya, im sorry if this has no revelance, but im desperate. Can anyone tell me (in the simplest form possible) how to do the inverse of a 3x3 matrix??FP3 exam 2moro....not a clue on anythin!! please helpI know how to get the determinant, but how do i get the matrix of minors? i also know how to get the matrix of cofactors....etc etc....   
  This sounds very like homework to me :P. Look it up in your maths textbook! ... that's all anyone here would post anyway.If you're trying to write a program to do it, use a maths library and call Matrix.Invert or similar ;).   ;  arghhh! its not homework!!! and i have looked it up and cant find it!!!!   ;Quote:Original post by xsarahxand i have looked it up and cant find it!!!![google]: "matrix inverse"1st link:http://mathworld.wolfram.com/MatrixInverse.html-me   ;  Read this:http://en.wikipedia.org/wiki/Matrix_inversion;  What's FP3?   ;  Further Pure 3....its a module in Further Mathematics...and thanks, im still none the wiser, but i appreciate the help :-)   ;  I see a couple of people beat me to it while I was writing this but I hope this helps you a bit.Let's say we have a 3x3 matrix A.One way to find the inverse of A is to augment the matrix with the identity matrix so you have[a11 a12 a13 | 1 0 0][a21 a22 a23 | 0 1 0][a31 a32 a33 | 0 0 1]and then reduce A to the identity matrix by row operations(Gauss-Jordan elimination). After doing this the 3x3 on the right, where the identity matrix originally was, is now the inverse of A.An example for a 2x2 matrix(it should be no problem extending this to 3x3).A =[ 1 2 ][ 3 4 ]Now we augment it with the 2x2 identity matrix and perform Gauss-Jordan elimination.[ 1 2 | 1 0][ 3 4 | 0 1]row2 = row2 - 3 * row1----->[ 1 2  |  1 0][ 0 -2 | -1 1]row2 = row2 / (-2)----->[ 1 2 | 10  ][ 0 1 | 3/2  -1/2]row1 = row1 - 2 * row2----->[ 1 0 | 01  ][ 0 1 | 3/2  -1/2]Now the inverse of A should be:A^1 =[ 01  ][ 3/2  -1/2]and the following should hold: A * A^-1 = I = A^-1 * AI hope this helps you. Good luck with your exam.- JesperEDIT: Also check Gauss-Jordan Elimination -- from Wolfram MathWorld;  Hiya, thank you soooo much!!we dont do the Gauss-Jordan elimination, but the theory we do is similar. I think ive got it sorted now, just need to do vectors....argh!!again, thanks!!! i really do appreciate it!! :-) x   