1. The problem statement, all variables and given/known data(adsbygoogle = window.adsbygoogle || []).push({});

Determine which of the formulas hold for all invertible nxn matrices A and B

1. (In-A)(In+A) = In - A^2

2. (A+B)(A-B) = A^2 - B^2

3. A^8*B^5 is invertible

4. (A+A^-1)^9 = A^9 + A^-9

5. AB = BA

6. A+A^-1 is invertible

I know 5 is right, and number 2 wrong, but what else?

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Linear Algebra-Inverses

**Physics Forums | Science Articles, Homework Help, Discussion**