1. a simple matrix question

if norm(AX)>=c*norm(X), for all X in Rn, and c>0
then how to get: if AX=0, then X=0??
thanks!!!
I got it , sorry for bothering

2. Originally Posted by violetsf
if norm(AX)>=c*norm(X), for all X in Rn, and c>0
then how to get: if AX=0, then X=0??
thanks!!!
I got it , sorry for bothering
norm(AX) >= c*norm(X) >= 0 because c>0 and norm(X)>=0.
So if AX=0 then 0>= c*norm(X) >= 0.