Is operation $x*y = \frac{xy}{x+y+1}$ associative?
61387
Incorrect Solution for Problem 7 of Pinter's Book of Abstract Algebra, Chapter 2?
58773
What does the operation c=a+++b mean?
1932
How to show this equality of $\rho(X,Y)$
16948
Need help with a proof that if $xy=0$ then $x=0$ or $y=0$
28286
About finding the function such that $f(xy)=f(x)f(y)-f(x+y)+1$
14161
Proof of when is $A=X^TX$ invertible?
67454
Show that $\sum_{i=1}^n (x_i - \bar{x})(y_i - \bar{y}) = \sum_{i=1}^n (x_i - \bar{x})(y_i)$.
59934
What is the term for a factorial type operation, but with summation instead of products?
108704
Help with proof of $|x+y| \geq |x|-|y|$
43599
Is the Ratio of Associative Binary Operations to All Binary Operations on a Set of $n$ Elements Generally Small?
79040
Graph of $|x| + |y| = 1$
55488
Proving that $\operatorname{codim}(X,Y)=\dim(\mathcal{O}_{X,\eta})$
52305
Is there a general relation between $a/b$ and $(a+c)/(b+c)$ where $a,b,c > 0 $?
66772
$f(f(x)f(y))+f(x+y)=f(xy)$
128764
How does $y[x] = a x^r$ when $y'[x] = \frac{(r y[x])}{x}$ and $y[1] = a$
118387
How to extend summations to fractional orders?
136782
Prove that $x * y = \frac{x+y}{1+xy}$ is a stable part of $G=(-1, 1)$