# Homework Help: Showing A Matrix Property Is True

1. Oct 19, 2012

### Bashyboy

1. The problem statement, all variables and given/known data
Let A be an invertible matrix. Show that $(A^n)^{-1} = (A^{-1})^n$

2. Relevant equations

3. The attempt at a solution
I want to begin on the left side of the equality sign; but I am having a little difficulty on expanding it. I started to--$(A^n)^{-1} = AAA...A^{-1}$--but it just didn't appear correct. Could someone help me?

2. Oct 19, 2012

### HallsofIvy

I would be inclined to prove it using "induction". If n= 1, this just says that $(A)^{-1}= A^{-1}$. Now, suppose $(A^k)^{-1}= (A^{-1})^k$. What can you say about $(A^{k+1})^{-1}= ((A^k)A)^{-1}$?

(You will need to prove separately that $(AB)^{-1}= B^{-1}A^{-1}$.)

By the way, you have
.
No, that is not correct. (An)-1 is the multiplicative inverse of An: (An)(An)-1= I.