Show that if A is positive definite, then both a & b are positive.
I think I'm on the right track with the following...
Can anyone point me in the right direction? Thanks.
I see. So the incompatibility with those values would stop it from being positive definite. I think I was looking at it from the wrong perspective. Rather than trying to find some z for which a and b wouldn't work unless they were both positive, I was looking more generally at a and b to make sure they always had to be positive for the inequality to hold true.
Thanks for the help.