Given matrix A below, calculate det[A] twice using minors and cofactors

A = \left[\begin{array}{ccc}1&2&3\\3&4&5\\6&7&8\end{array}\right]

Pivot on:

a) row 2, and also

b) column 3

Given matrix A below, calculate det[A] twice using minors and cofactors

A = \left[\begin{array}{ccc}1&2&3\\3&4&5\\6&7&8\end{array}\right]

Pivot on:

a) row 2, and also

b) column 3

Answer:a. 3(16-21) – 4(8-18) +5(7-12) = -15 + 40 – 25 = 0

b. 3(21-24) – 5(7-12) + 8(4-6) = -9 + 25 – 16 = 0