What is adj(A) in this problem?
This is the adjugate, where adj(A)/det(A) = inv(A). For a 2x2 matrix, $[a~~b; c~~d]$, the adjugate is $[d~~-b; -c~~a]$.
What is adj(A) in this problem?
This is the adjugate, where adj(A)/det(A) = inv(A). For a 2x2 matrix, $[a~~b; c~~d]$, the adjugate is $[d~~-b; -c~~a]$.