# List five elements in each of the following sets:

• Mar 12th 2013, 03:41 AM
rtrumpow
List five elements in each of the following sets:
I am lost in Discrete Mathematics. I do not know what is being asked for these two questions.

List five elements in each of the following sets:
2d.) {n Î N | n2 + n is a multiple of 3}

List the (distinct) elements in each of the following sets:
1b.) {x Î Z | xy = 15 for some y Î Z}

I would like verification if this is accurate:
9a.) List all the subsets of the set {a,b,c,d} that contain:
i.) four elements - {a,b,c,d}
ii.) three elements - {a,b,c}, {a,b,d}, {a,c,d}, {b,c,d}
iii.) two elements - {a,b}, {a,c}, {a,d}, {b,c}, {b,d}, {c,d}
iv.) one element - {a}, {b}, {c}, {d}
v.) no elements - {0}
• Mar 12th 2013, 03:46 AM
jakncoke
Re: List five elements in each of the following sets:
2d) list 5 natural numbers of the form \$\displaystyle n^2 + n = 3p \$ for some integer \$\displaystyle p \$ so one would be \$\displaystyle 3^2 + 3 = 12 = 3 * 4 \$

1b) list all the x's such that x*y = 15, for some integer y. so one element of the set is 3, since 3*5 = 15., another is -3, since -3*-5 = 15

9a)correct.
• Mar 12th 2013, 07:30 AM
rtrumpow
Re: List five elements in each of the following sets:
Thank you for you assistance and explanations. I am still new to this whole Discrete Mathematics and struggling a bit. The explanations helped to put these questions into perspective.