Is there a function $y=f(x)$ such that $\frac{d^3y}{dx^3} = f(x)$?
107609
Function whose third derivative is itself.
28286
About finding the function such that $f(xy)=f(x)f(y)-f(x+y)+1$
85076
Is it true that $d(x,Y)=d(x,y_0)$ for some $y_0 \in Y$ when $Y$ is closed?
126931
Find $f(x)$ such that $f(x)+f\left(\frac{1}{x}\right)=f(x)\cdot f\left(\frac{1}{x}\right)$
11453
Find a real function $f:\mathbb{R}\to\mathbb{R}$ such that $f(f(x)) = -x$?
86128
Find all functions $ f : \Bbb R \to \Bbb R$ which satisfy $f(x)f(y) = f(x + y) + xy$ for all $x, y ∈ \Bbb R$.
60878
How to prove that $\lim_{(x,y) \to (0,0)} \frac{x^3y}{x^4+y^2} = 0?$
106830
are $f(f(x))=f(x)$ and $f(x)=x$ equivalent?
99917
What function satisfies $F'(x) = F(2x)$?
10068
$f(x,y)= e^{-\frac{1}{x^2+y^2}}$ when $(x,y)\neq (0,0)$ and $f(0,0)=0$.
62529
Solve $y’ = \frac{2-xy^3}{3x^2y^2}$ using Bernoulli form
107400
Can there be an injective function whose derivative is equivalent to its inverse function?
157920
Can I define $y=y(x)$?
32599
Solution to the functional equation $f(x^y)=f(x)^{f(y)}$
62966
Find all functions $f(x)$ such that $f\left(x^2+f(y)\right)$=$y+(f(x))^2$
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 $f(1) = 3$
81720
$f(x) + f(x+f(y)) = y + f(f(x) + f(f(y)))$