Trying to solve $f(x)f(y) = f(x + y)$
11828
continuous functions on $\mathbb R$ such that $g(x+y)=g(x)g(y)$
73519
Determine all functions satisfying $f(x + f(x + y)) + f(xy) = x + f(x + y) +yf(x)$
23485
Solving $\forall x \in \mathbb{R}_+^*, f'(x) = f\left(\frac1{x}\right)$
32599
Solution to the functional equation $f(x^y)=f(x)^{f(y)}$
121455
$f(x)$ if $f(xy)=f(x) +f(y) +\frac{x+y-1}{xy}$
117353
Polynomial equation $f(x)f(2x^2)=f(2x^3+x)$
13248
How to obtain $f(x)$, if it is known that $f(f(x))=x^2+x$?
81720
$f(x) + f(x+f(y)) = y + f(f(x) + f(f(y)))$
86367
Computing $f(x)$ if $\int_1^{xy} f(t) dt = y \int_1^x f(t) dt + x\int_1^y f(t) dt$ and $f(1) = 3$
48652
Solve the functional equation $2f(x)=f(ax)$ for some $a$.
27809
Find the function equation $f(x+f(y)+yf(x))=y+f(x)+xf(y)$
157744
Cauchy's functional equation with composite function: $gf(x+y)=gf(x)+gf(y)$
142873
What does the function f: x ↦ y mean?
1071
Determine all functions $f:\mathbb{N}\rightarrow\mathbb{N}$ such that $xf(y)+yf(x)=(x+y)f(x^2+y^2)$ for all $x,y\in\mathbb{N}$ (contest question)
37976
Find all functions $f$ such that $(x+y)f(x)+f(y^2)=(x+y)f(y)+f(x^2)$
49794
Solve $f(x^2+y+f(y))=2y+f(x)^2$ over $\mathbb{R}$
29647
Do there exist functions satisfying $f(x+y)=f(x)+f(y)$ that aren't linear?