# Thread: A few questions on graphs I've attempted but not sure if they're correct

1. ## A few questions on graphs I've attempted but not sure if they're correct

which I've drawn on paper

thanks

2. ## Re: A few questions on graphs I've attempted but not sure if they're correct

I notice you have not given an answer to (a) which is necessary for b while for (b) it looks like you have drawn precisely those edges that are not in E! Edge set E is defined as $\displaystyle \{(i, j)| A_i\cap A_j= \phi\}$. (1, 2) is NOT in that set because $\displaystyle A_1\cap A_2= {2}$ and is not empty. Similarly (2, 3), (3, 4), (4, 5) and (1, 5) are not edges but (1, 3), (1, 4), (2, 4), (2, 5), and (3, 5) are. The graph is not a pentagon but the a five pointed star.

3. ## Re: A few questions on graphs I've attempted but not sure if they're correct

Thanks HallsofIvy ,
I think I'm having a bit of trouble reading the question. the part E = {{ i,j } : i,j ∈ V , Ai ∩ Aj = Ø}
in words E equals in the set i,j i,j is an element of V , Ai is disjoint to Aj = to the empty set .
I'm struggling with the i and j part as i don't know what they are there for .
Thanks again

4. ## Re: A few questions on graphs I've attempted but not sure if they're correct

Originally Posted by bee77
Thanks HallsofIvy ,
I think I'm having a bit of trouble reading the question. the part E = {{ i,j } : i,j ∈ V , Ai ∩ Aj = Ø}
in words E equals in the set i,j i,j is an element of V , Ai is disjoint to Aj = to the empty set .
I'm struggling with the i and j part as i don't know what they are there for .
Thanks again
Here is the graph.
Note that the graph is $\mathscr{K}_5\setminus\mathscr{P}_5$, the complete graph order five minus the standard Pentagon.
You need to completely redo the required matrices.

5. ## Re: A few questions on graphs I've attempted but not sure if they're correct

Thanks Plato ,
I'll do the matrices a bit later and post them for the star you have just drawn ,right now working on some other problems associated with graphs and discrete math .

cheers

6. ## Re: A few questions on graphs I've attempted but not sure if they're correct

I just did the adjacency matrix and incidence matrix
Thanks for the help with the star graph .
Those look ok right ?

Thanks