This question already has an answer here:
I answered three question a while back, and today when I logged-in I see they were all voted down in chronological order. In fact one of my answers was even accepted by OP.
Refer to these links:
proof that $A \triangle (B \triangle C) = (A \triangle B) \triangle C$
what is the cardinality of $\{n^{1/k}: n, k\in \mathbb{N}\}$?
Were my answers deficient? As far as I know, they are all rigorous. Are there criteria for downvoting answers, like there are for questions? Were my answers not on par with the criteria?
Regards!