Oh I forgot to mention the answer says that it is

(14..25)
(5....9 )
^ sorry if that doesn't look right
it's supposed to be a matrice

2. Originally Posted by positiveion

Oh I forgot to mention the answer says that it is

(14..25)
(5....9 )
^ sorry if that doesn't look right
it's supposed to be a matrice
You're meant to realise that the result of AB tells you that $B^{-1} = A$ ....

Then $BC = A \Rightarrow B^{-1} B C = B^{-1} A \Rightarrow C = B^{-1} A = A^2$.

3. wait, why does that equal A^2

4. Originally Posted by positiveion
wait, why does that equal A^2
You're meant to join the dots. Substitute $B^{-1} = A$.