Given an invertible matrix $A$ such that all elements in $A$ and in $^{−1}$ are integers, find $|^4|$ I find this question very interesting, but I am having trouble figuring out how to approach the problem. 
I know that the $\det(A^{-1}) = 1/\det(A)$, but I'm unsure of where to go from here.
If someone can send me in the right direction, it would be very much appreciated. 
Thanks in advance, 
Tommy.

Hint: If $A \in M(n,\mathbb Z)$ is invertible then $\det(A)=\pm 1$.
