Just a simple question I want to know how to do, google hasn't been a help.
Show that A + 0 = A
Is it something like, make A a 1 so its 1 + 0 = 1?
Is A a matrix? If so, are you working over arbitrary field, over reals...?
Nevertheless, to verify this for matrices you just have to look at each position, you get equality $\displaystyle a_{i,j}+0=a_{i,j}$, which is valid in any field (in particular, in reals).
However, it was just a guest that you mean matrices - you should have specified the context of your question.