# How can we proof this matrix norm equality?

1. Dec 18, 2011

### JohnNL

||A-1|| = max ||x|| / ||Ax|| x$\in$ℝn, x≠0 . x is a vector.

2. Dec 18, 2011

### mathwonk

well try the reciprocal one, for the norm of A. (operator norm of course, assuming you know the definition. that's the place to start of course.)