assuming you know how to transpose a matrix and fin the determinant:
inverse of 2x2 matrix is 1/determinant[matrix transposed]
3x3 matrix is 1/determinant[adjugate matrix]
does it work? i dont seem to get the answer in the book? its gettin late in the uk lol.
3x3 matrix
first find the determinant.
R1 is 1 0 1
R2 2 1 3
R3 -1 1 1
this is 1(1-3)-0(-3-2)+1(2--1)
=-2-0+3
=1
Now find all the minor determinants of each element.
R1 -2 0 3
R2 -1 2 1
R3 -1 1 1
then add a minus sign to each of the even numbered elements.
R1 -2 -0 3
R2 +1 2 -1
R3 -1 -1 1
Transpose the matrix
R1 -2 1 -1
R2 0 2 -1
R3 3 -1 1
now multiply by the 1/determinant found at the beginning
1 * New Matrix
hope this helps,
more importantly i hope this is right lol