نمایش ریاضی $A=\{3\,,\,-6\,,\,9,\,-12\,,\,...\}$ کدام است؟
1 )
$\{{{(-1)}^{n+1}}\times 3(n+1)\,\left| n\in W \right.\}$
$\{{{(-1)}^{n+1}}\times 3n\,\left| n\in \mathbb{N} \right.\}$
3 )
$\{{{(-3n)}^{n+1}}\,\left| n\in W \right.\}$
4 )
$\{3{{(-n)}^{n+1}}\,\left| n\in \mathbb{N} \right.\}$