00:01
Welcome back to another discrete structures problem with a universal quantifiers question.
00:07
We're told that n of x is the statement x has visited north dakota, where x belongs to your school.
00:16
And we're going to try and use these three quantifiers in order to tell us what these various statements mean.
00:24
This backwards e means there exists.
00:26
This upside down a means for all.
00:29
And this little hyphen thing means not or negation.
00:32
It undoes whatever the next symbol is.
00:35
That means a says there exists an x, and then we're going to include the word such that in between.
00:45
There exists an x such that x has visited north dakota.
00:51
Or in plain english, there is a student in our school who has gone to north dakota.
00:56
Similarly, this upside down a means for all, so for all x, x has visited north dakota, or every student in the school has gone to north dakota.
01:12
When we have not, there exists, you can look at that as there does not exist.
01:19
There does not exist an x such that x has visited north dakota.
01:26
So there are no students in the school who have visited north dakota...