Of course you can’t correct every typo you make. But now it was in the heart result of the previous post so it must be corrected. In the previous post I showed you a way of calculating the determinant of a 4×4 matrix using 2×2 minors. As such I used things like a ‘complementary minor’ inside a square matrix.
The typo is easy to understand, it must not be comp(| AB₁₂ |) but this:
| comp( AB₁₂)|. The vertical stripes mean you must take the determinant of what’s between them so the typo is that I took the determinant too fast. First you must find the complementary minor and after that take the determinant…

This correctional post is two pictures long, first I show you the faulty one and after that the correct one.

My guess is most readers who tried to understand the previous update did find for themselves it was very faulty. But I could not just ignore it because it was in the main result although the main result is not earth shaking math. Anyway it is what it is and now it’s corrected.