Question

The element in the first row and third column of the inverse of the matrix $\begin{bmatrix} 1 & 2 & 3 \\ 0 & 1 & 2 \\ 0 & 0 & 1 \end{bmatrix}$ is

• A. 1
• B. – 2
• C. 0
• D. None of these

Answer 1

Answer: (A)

1

Answer 2

a₁₃ of A^–1

= $\frac{C_{31}}{|A|}$ = $\frac{\left| \begin{matrix} 2 & 3 \\ 1 & 2 \end{matrix} \right|}{1}$ = 1