# List the (distinct) elements in each of the following set:

• Mar 13th 2013, 02:33 AM
rtrumpow
List the (distinct) elements in each of the following set:
I am not sure what these problems are requesting. I have watched Discrete Math videos and read my textbook, still unable to arrive at the answers.

List the (distinct) elements in each of the following set:
1e.) {aÎN | a < -4 and a > 4}

Let A = {(-1,2), (4,5), (0,0), (6,-5), (5,1), (4,3)}
List the elements in each of the following sets.
3b.) {a | a > 0 and (a,b) Î A for some b}

4.) List the elements in the sets A={a,b) Î N x N | a≤b, b≤3} and B={a/b Î {-1,1,2} }.
• Mar 13th 2013, 09:04 AM
HallsofIvy
Re: List the (distinct) elements in each of the following set:
Quote:

Originally Posted by rtrumpow
I am not sure what these problems are requesting. I have watched Discrete Math videos and read my textbook, still unable to arrive at the answers.

List the (distinct) elements in each of the following set:
1e.) {aÎN | a < -4 and a > 4}

You can't, strictly speaking, list the elements because there are an infinite number of them. Is it possible that the problem actually said "a> -4" and "a< 4"? In addition, "N" usually means the positive integers. If that is the case here, the reference to "-4" is irrelevant.

Quote:

Let A = {(-1,2), (4,5), (0,0), (6,-5), (5,1), (4,3)}
List the elements in each of the following sets.
3b.) {a | a > 0 and (a,b) Î A for some b}
The only requirement is that "a> 0" and only (-1, 2) and (0, 0) don't satisfy that.

Quote:

4.) List the elements in the sets A={a,b) Î N x N | a≤b, b≤3} and B={a/b Î {-1,1,2} }.
If "\$\displaystyle a\le b\$", a/b can't be 2. And "a/b= -1" isn't possible for for a and b both positive numbers. That leaves only "a/b= 1" and b can only be 1, 2, or 3.
• Mar 13th 2013, 09:12 AM
rtrumpow
Re: List the (distinct) elements in each of the following set:
Question 1e.) is accurate. I verified with the textbook that I did not switched the signs.
• Jan 23rd 2015, 10:52 AM
laurm
Re: List the (distinct) elements in each of the following set:
I'm really confused with question 4. My textbook shows B= {a/b | a,b belongs to {-1,1,2}} I thought that the sets A= and B= would be two different answers but they're all one? This discrete math is killing me please help
• Jan 24th 2015, 03:06 PM
emakarov
Re: List the (distinct) elements in each of the following set:
Quote:

Originally Posted by laurm
My textbook shows B= {a/b | a,b belongs to {-1,1,2}}

This means all possible expressions of the form \$a/b\$ where \$a\$ and \$b\$ range over \$-1\$, \$1\$ and \$2\$.