Find U n is an element of the natural numbers An' and the...

[Enh0702]

Assume the universe of discourse is is the set of all natural numbers.
Find U n is an element of the natural numbers An' and the Intersection.

a) An={7,n}

b)An={k is an element of natural numbers: K=>n}

In An n is a subscript

=> this means greater than or equal to.
I know when finding the complement in letter b k<=n. Does that mean that the union would be all natural numbers for a and the intersection would be 7? My book doesn't do a good job explaining how to do this.

 

[pka]

Your notation is exceedingly hard to read.
Is the part (a) this?
\(\displaystyle \L \bigcup\limits_{n \in N } {\left\{ {7,n} \right\}}\)??

 

[Enh0702]

yes it is sorry I don't know where the symbols keys are

 

[pka]

yes it is sorry I don't know where the symbols keys are

There are no symbols keys.
It is LaTeX. You can use it with help on the Forum Help tab above.

But in the meantime tell us what you problem says.

 

[Enh0702]

It is what is the complement of the union and intersect of An={7,n} when n is an element of the natural numbers. It is what you wrote out in symbols before I need to take the complement of it.

 

[stapel]

It is what is the complement of the union and intersect of An={7,n}...

"The union and the intersection of A_n" with what?

Eliz.

 

[pka]

Assume the universe of discourse is is the set of all natural numbers.
Find U n is an element of the natural numbers An' and the Intersection.
b)An={k is an element of natural numbers: K=>n}

I am going to take a guess as to what part b is about (still cannot understand part a).
\(\displaystyle \L \begin{array}{l}
A_n = \left\{ {k \in N:k \ge n} \right\} \\
\bigcup\limits_{n \in N} {A_n } = N\quad \& \quad \bigcap\limits_{n \in N} {A_n } = \emptyset \\
\left( {\bigcup\limits_{n \in N} {A_n } } \right)^c = \bigcap\limits_{n \in N} {\left( {A_n } \right)^c } = \emptyset \quad \& \quad \left( {\bigcap\limits_{n \in N} {A_n } } \right)^c = \bigcup\limits_{n \in N} {\left( {A_n } \right)^c } = N \\
\end{array}.\)