Which of the following holds: $ \bigcup x \in x ,\quad \bigcup x = x ,\quad x\in \bigcup x $ ,when:
(a) $x$ is a set, (b) $x$ is an ordinal.
Can someone help me?
Thank you in advance!
Which of the following holds: $ \bigcup x \in x ,\quad \bigcup x = x ,\quad x\in \bigcup x $ ,when:
(a) $x$ is a set, (b) $x$ is an ordinal.
Can someone help me?
Thank you in advance!