This is a true or false question, hence are the answers supposed to follow quickly? Because the empty set has no identity element, hence $\emptyset$ is not a group. Hence I'm inquiring for intersection and union $\neq \emptyset$.
Because the intersection of subgroups is a subgroup, I guessed intersection of groups is truly a group? But Fraleigh's answer says false?
I inquired about the union of subgroups is not a subgroup, but what about for groups? I don't know how to predestine, preordain this because that other question, for sub groups, still feels "fatidic" or magical to me. To boot, the difference, for the intersection of subgroups vs that of groups, confounds me as to what to do. What's the intuition?
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