کدام یک از مجموعههای زیر، تهی است؟
1 )
$\left\{ \left. \sqrt{-x}\left| x\in \mathbb{Z},x \lt 0 \right. \right\} \right.$
2 )
$\left\{ \left. x\left| x\in \mathbb{Z},{{5}^{x}}={{2}^{x}} \right. \right\} \right.$
3 )
$\left\{ \left. x\left| x\in \mathbb{Z},-x \gt x \right. \right\} \right.$
$\left\{ \left. x\left| x\in \mathbb{Z},{{x}^{2}}+1=0 \right. \right\} \right.$