Question

Please Help. Inverse Matrices

Answer 1

2x2 matrixes have a nice visual method:

a b inverts to d -b divide byt he determinant
c d -c a

Answer 2

swap two corners, negate the other corners; divide byt he determinnt of the original matrix

Answer 3

\[A = \left[\begin{matrix}a & b \\ ? & d\end{matrix}\right]\]\[A^{-1} = \frac{ 1 }{ detA }\left[\begin{matrix}d & -b \\ -c & a\end{matrix}\right]\]

Answer 4

should be c instead of ?

my c button is stuck or something

Answer 5

I found it it was C

Answer 6

I believe at least

Answer 7

C is fine .. det = 8, and 6/8 is not an integer