3 2 -1

Question

Matrix A = 0 4 -6
2 -1 3
i)Expand and evaluate detA using minors of the first row elementary.
ii) Write down the expansion of detA using cofactors of the second column elements.

Answer 1

| 3 2 -1 |
| 0 4 -6 |
| 2 -1 3 |

Answer 2

a) 3(12 - 6) - 2(0+12) + (-1)(0 - 8) = ....
b) remember that the signs go +, -, +, -, etc
so how does the 2nd row start?

Answer 3

The + and - alternate in both directions.
Time to review the section, yeah?