Question

Find the determinate of the matrix by expansion of co-factors through (a) row 1, (b) column 2. The answers for both should be -75. The matrix is as follows:

-3 2 1
4 5 6
2 -3 1

I got the following minors and co-factors, some of which may be wrong.
M(1,1) = Minor: row 1, column 1
C(2,1 )= Co-factor: row 2, column 1

M(1,1) = 23
M(1,2) = -8
M(1,3) = -22
M(2,1) = 5
M(2,2) = -5
M(2,3) = 5
M(3,1) = 7
M(3,2) = -22
M(3,3) = -23
C(1,1) = 23
C(1,2) = 8
C(1,3) = -22
C(2,1) = -5
C(2,2) = -5
C(2,3) = -5
C(3,1) = 7
C(3,2) = 22
C(3,3) = -23

Answer 1

unbelievable!!! admire you.

Answer 2

what?

Answer 3

expansion of cofactors is you take your matrix right do you follow that?