Discrete Math

[discretec]

Instructions: List 5 elements in the following set.
Problem: {n belongs to N such that n^2+n is a multiple of 3}
N being natural numbers.
My answer: {3,6,9,12,15}
On the answer key it says the answer is {2,3,5,6,8}. Are my answers also correct? Are there numerous answers that could be correct?
Thanks for any help. So far this forum is proving to be an extremely helpful learning environment.
C

 

[daon]

Yes, your answer is correct also. Note that if n is any multiple of 3 then n(n+1)=n^2+n is obviously a multiple of 3 also.

 

[discretec]

Thank you.
C

 

[Deleted member 4993]

Instructions: List 5 elements in the following set.
Problem: {n belongs to N such that n^2+n is a multiple of 3}
N being natural numbers.
My answer: {3,6,9,12,15}
On the answer key it says the answer is {2,3,5,6,8}. Are my answers also correct? Are there numerous answers that could be correct?
Thanks for any help. So far this forum is proving to be an extremely helpful learning environment.
C

Either n or (n+1) is multiple of 3.