$AB=A+B$ implies $AB=BA$
6096
If $A+B=AB$ then $AB=BA$
25907
Show $a\Bbb Z+b\Bbb Z = \gcd(a,b)\Bbb Z$
74631
For natural numbers $a$ and $b$, show that $a \Bbb Z + b \Bbb Z = \gcd(a, b)\Bbb Z $
21726
Show that if $(b,c)=1$, then $(a,bc)=(a,b)(a,c)$.
63931
When $ab/(a+b)$ is an integer, where $a,b$ are positive integers.
13026
Prove that if AB=I_m, then rk(A)=rk(B).
64108
how to prove $a+b-ab \le 1$ if $a,b \in [0,1]$?
130281
Proving $a^ab^b + a^bb^a \le 1$, given $a + b = 1$
60707
Show that if $ \ A \cup B = A$ and $ \ A\cap B = A$ then $ \ A = B$
26570
Prove $\operatorname{rank}(AB) = \operatorname{rank}(B)$
145876
$AB-BA=A$ implies $A$ is singular and $A$ is nilpotent.
74460
Matrices A+B=AB implies A commutes with B
141173
Are there matrices such that $AB=I$ and $BA \neq I$
45760
if G is generated by {a,b} and ab=ba, then prove G is Abelian
128820
Prove that if $\gcd(a,b)=1$ then $\gcd(ab,c) = \gcd(a,c) \gcd(b,c)$
66709
Are the matrix products $AB$ and $BA$ similar?
10348
Prove that if the $\gcd(a,b)=1$, then $\gcd(a+b,ab)=1$