x Turn on thread page Beta
 You are Here: Home >< Maths

# Matrix proof watch

1. proof that for any matrices A and B. AB=I implies BA=I

i don't know what to do. any help.
2. (Original post by user6)
proof that for any matrices A and B. AB=I implies BA=I

i don't know what to do. any help.
well it is not true in general. Maybe A,B are square matrices?
3. (Original post by tombayes)
well it is not true in general. Maybe A,B are square matrices?
what is a square matrix? anyway surely AB=I obviously implies BA=I
e.g. 3 times 1/3=1=1/3 times 3. Surely AB always is equal BA.
4. (Original post by user6)
what is a square matrix? anyway surely AB=I obviously implies BA=I
e.g. 3 times 1/3=1=1/3 times 3. Surely AB always is equal BA.
a square matrix has same number of row and columns. And no for matrices AB is not always equal to BA, can you find an example?

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: January 14, 2015
Today on TSR

### Is uni even worth it?

Does anyone use their degree?

Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams