something i still unclear on ideal test..
since there are two conditons in ideal test 1. a-b in A whenever a, b in A 2.ra and ar are in A whenever a in A and r in A
i just wonder when i use the ideal test, i need to use both condtions together
or just use one of both , then i can conclude a nonempty subset of a ring R is an ideal of R
thx I would think both need to be satisfied. Sorin.c