0
$\begingroup$

$A=\{7,14,21,28\}$ is the set-builder notation $\{x \in \mathbb N:x=7n, n \in \mathbb N \text{ and } 1\le n \le 4\}$ right?

$\endgroup$
  • $\begingroup$ A={7,14,21,28} (it's not a sequence). It looks correct to me. I would probably use $\land$ instead of comma or descriptive text ("and") though. Not sure if it is necessary with things like $\forall$ etc, guess it depends on the formality level. $\endgroup$ – Emil Feb 19 '16 at 9:41
  • $\begingroup$ Wellcome to MSE !! $\endgroup$ – HK Lee Feb 19 '16 at 9:45
  • $\begingroup$ It is indeed correct but it does carry some redundancies (you've said that $n \in \mathbb{N}$, which already means that $x=7n \in \mathbb{N}$, so saying prior to that that $x \in \mathbb{N}$ is unnecessary). $\endgroup$ – Irregular User Feb 19 '16 at 10:14
0
$\begingroup$

Yes, it is correct.

See also The following questions with answers, where more set builder notation very similar examples are discussed: This, This and Especially This.

| cite | improve this answer | |
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.