you misunderstaood it.i don't like number theory,but it doesn't mean that i hate it or don't do it from time to time.i have a little of number theory in every grade.
]]>Did you not say that you did not like number theory?
]]>http://en.wikipedia.org/wiki/Empty_set
There is only one of them.
]]>just a question:
should it be 'an empty set' or 'the empty set'?