New posts in Functional Equations

Recreational math: If $f(f(x))=e^x$, bound the integral $\int_0^1 f(x)dx$

Find all solutions to $f(x+f(x))=2x$

Solving the functional equation $f(n^2+m)=f(n+m^2)$

Does there exist a nontrivial rational function which satisfies $f(f(f(f(x))))=x$?

When does $f(X) = g(X+1)-g(X)$ where $f, g \in \mathbb{C}(X)$?

$f\circ g(x)$ and $g\circ f(x)$ are given; find $f$ and $g$

Find all $f$ that satisfies $f:\mathbb{R}\rightarrow\mathbb{R};f(x+y)+f(x)f(y)=(1+x)f(y)+(1+y)f(x)+f(xy)$

What is the value of $f(100)$?

Functional equation: what function is its inverse's reciprocal?

Continuous $f$ such that $f(x)=f(x^2)$ is constant?