Question

I need help figuring out how this problem was solved. (Image to follow)

I reduced det(2adj(C^(-1))) using these steps:
1. det(2adj(adj(C)/det(C)))
2. det(2adj(adj(C))/det(C))
3. det(2C/det(C))
4. (1/2)det(C)det(C)

Solving the detrminant algebreically using the ad-bc formula gave me det(C) = -3. When I plug this into my equation, it gives me (9/2), which is wrong.

Am I going about this the wrong way?

Answer 1

Here's the problem

Answer 2

Figured it out. It's rather complicated.