# Rank, Co-factor matrices.

## Homework Statement

Let A be an n x n matrix where $n \geq 2$. Show that $A^{\alpha} = 0$ (where $A^{\alpha}$ is the cofactor matrix and 0 here denotes the zero matrix, whose entries are the number 0) if and only if $rankA \leq n-2$

## The Attempt at a Solution

No idea where to start with this, it's just an additional question in the lecture notes which I haven't gone through in tutorial. Thanks.