This question has confused me a bit.
Find nonzero 2x2 matrices A and B such that AB=0.
I've been just trying to find two 2x2 matrices who result in a 2x2 matrix with 0 at each position.
The answer I got is
A =
1 1
1 1
B=
1 1
-1-1
so AB =
0 0
0 0
I think that is correct, but the question ased for AB=0, does that mean a matrix with 0 in all positions?