On the equation $f(x^2+y+f(y))=2y+f(x)^2.$
49794
Solve $f(x^2+y+f(y))=2y+f(x)^2$ over $\mathbb{R}$
96185
Solutions of $x^2+y^2+z^2 = n$ in $\mathbb{Z}_2$.
98255
Find $f(x)$ such that $f(f(x)) = x^2 - 2$
68409
Consider $f(x,y)=\sup_{θ,φ}\{||e^{i θ }x+ e^{i φ }y||^2: θ,φ∈R\}$ in which $x,y\in\mathbb C^n$
144090
How to solve the functional equation $f\left(x^2+f(y)\right)=y+f(x)^2$
31732
If the function $f$ satisfies the equation $f(xf(y)+x)=xy+f(x)$, find $f$
121455
$f(x)$ if $f(xy)=f(x) +f(y) +\frac{x+y-1}{xy}$
71756
diophantine equation: $x^2 +y^2 = z^n$
66772
$f(f(x)f(y))+f(x+y)=f(xy)$
136475
d'Alembert-like functional equation: $f(x+y)+g(x-y)=\lambda f(x)g(y)$
72023
Integer solutions of the equation $x^2+y^2+z^2 = 2xyz$
88683
Functional equation $f\left(\frac{x+y}{2}\right)+f\left(\frac{2xy}{x+y}\right)=f(x)+f(y)$ implies $2f(\sqrt{xy})=f(x)+f(y)$
4178
Solve $f(x)f(2x^2) = f(2x^3+x)$
77763
Proof that the equation $x^2 - 3y^2 = 1$ has infinite solutions for $x$ and $y$ being integers
28286
About finding the function such that $f(xy)=f(x)f(y)-f(x+y)+1$
32599
Solution to the functional equation $f(x^y)=f(x)^{f(y)}$
24862
Solving (quadratic) equations of iterated functions, such as $f(f(x))=f(x)+x$