prove that (Ha)(Hb)=Hab iff H is normal
56245
Let H be a subgroup of a group G. Prove that the following statements are equivalent.
1251
If $[G:K]$ is finite, then $[H:H \cap K] = [G:K]$ iff $G = HK$ (Hungerford Proposition 4.8, Proof)
44453
Prove that the normalisation of $A=k[X,Y]/(Y^2-X^2-X^3)$ is $k[t]$ where $t=Y/X$ (Reid, Exercise 4.5)
28108
Proving the kernel is a normal subgroup.
27281
How to prove $\,x^a-1 \mid x^b-1 \iff a\mid b$
78463
Prove that $\sup \{-x \mid x \in A\} = -\inf\{x\mid x \in A\}$
116215
Prove that $P(A \cap B\mid C)=P(A \mid (B \cap C))P(B\mid C)$
43310
Proving $A\cap(B-C)$ is equal to $(A\cap B)-(A\cap C)$
152817
Proving $\sup B=\inf A$
42355
Double check $G\sim H$ iff $G≈H$
12802
Proof of correctness of normal equation
28722
Prove that $H$ is a abelian subgroup of odd order
106779
How to show if $H,K$ are normal subgroups in a group $G$ then $[H,K] \leq H \cap K$
104949
How would I prove that this function is affine if $f(x+h)-f(x)=hf'(x)$?
43913
Prove that if $A^*+A=AA^*$ then $A$ is normal
124179
Proof that every metric space is normal
129480
Prove that inf(A+B) = infA + infB