How to find the Domain , Range , matrix for the relation R

[zuhaira35]

can anyone help me ?
i have a homework and i did't find any answer for it

the question is

find the Domain , Range , matrix and the digraph for the relation R

a ) A = { 1,2,3,4,8 } = B , aRb if and only if a=b

b) A = { 1,2,3,4,6 } =B , aRb if and only if a multiple of b

 

[Greg]

Hello zuhaira35 and welcome to MHB! :D

We ask that our users show their progress (work thus far or thoughts on how to begin) when posting questions. This way our helpers can see where you are stuck or may be going astray and will be able to post the best help possible without potentially making a suggestion which you have already tried, which would waste your time and that of the helper.

Can you post what you have done so far?

 

[HallsofIvy]

can anyone help me ?
i have a homework and i did't find any answer for it

the question is

find the Domain , Range , matrix and the digraph for the relation R
a ) A = { 1,2,3,4,8 } = B , aRb if and only if a=b
b) A = { 1,2,3,4,6 } =B , aRb if and only if a multiple of b

If I had to do a problem like this, the first thing I would do is look up the definition of words I did not know! Do you know what "domain", "range", "matrix", and "digraph" mean here? Do you know what a "relation" is? Do you understand exactly what the relations referred to in (a) and (b) are?

A "relation" between two sets, A and B, (they may be the same set as here) is a collection of ordered pairs with the first member of each pair from A and the second from B. In (a) you are told that "aRb if and only if a= b" so it is the collection {(1, 1), (2, 2), (3, 3), (4, 4), (8, 8)}. Now, what are the "domain" and "range"?