Question

Please help with cofactors. I am confused because it asks twice for the cofactor of 1.

3x3 Matrix,

-1 3 6
1 6 1
-3 1 6

I got 35 for the first one, does that sound right?

Answer 1

I am trying to find the cofactor of 1, 6, and 1

Answer 2

is this furby town

Answer 3

they seem to be asking for the cofactors of the 2nd row 1 6 1
1 is in the (2,1) position (row 2 col 1) and 2+1=3 is odd. so the sign will be negative
now select out the submatrix by excluding the first column and the 2nd row
you are left with
3 6 (top row, cols 2 and 3)
1 6 (bot row, cols 2 and 3)

the det of this submatrix is 3*6-1*6= 18-6= 12

with the minus sign, the co-factor for 1 (in (2,1)) is -12