Question

alguem sabe resolver urgente

Answer 1

$A=\left[\begin{array}{ccc}1&2&3\\0&1&2\\2&-3&1\end{array}\right]$ 

Dp = 1+8+0
Ds = 6-6+0
Det (A) = 1+8-(+6-6)
Det (A) = 9-6+6
Det (A) = 9 
Det (A-¹) = $\frac{1}{9}$