Is it possible to prove that $x=\{x\}$ is false in ZF system?
121060
¿Can you help me with axiom of regularity?
111723
Can it be proven in $\sf ZF^{\neg\infty}$ that the sets $x_n=\{x_{n+1}\}$ do not exist?
143000
Show that there exists a $c\in \mathbb{C}$ such that $f(z)=c \bar{z}$ for all $\vert z\vert=1$.
15809
The problem of x = ln(x)
41779
Is $x/x$ equal to $1$
129232
Is there a name for an element $z$ such that $\,zx = z = xz\,$ for all $x$?
83713
If $z,w\in \mathbb{C}^{\times}$, then $|z+w|=|z|+|w|$ iff $w=tz$ for some $t\gt 0$
32589
Prove or disprove that Arg(zw)=Arg(z)+Arg(w)
113083
How to prove a set equality?
143735
Prove/Disprove: For any sets $X$ and $Y$, $\overline{X\cap Y} = \bar{X}\cup\bar{Y}$
40070
Is there a real-valued function $f$ such that $f(f(x)) = -x$?
106305
Prove/disprove: if $\det(A+X) = \det(B + X)$ for all $X$, then $A=B$
73415
The reason why the existence of inaccessible cardinals cannot be proven in ZFC
89637
Proof that in a field $x=0$ is equivalent to $x=-x$
134120
Prove statement with a counter-example: For all sets S, T and V, V ∪ (S ∩ T) = (V ∪ S) ∩ T is false
156252
Are sets constructed using only ZF measurable using ZFC?
31389
consistency of ZF\{Power Set axiom}