functional equation:$f(f(x))=6x-f(x)$
42699
Solve for $f(x)$ if $f(f(x))=6x-f(x)$
133646
real analysis -functional equation
35281
$1992$ IMO Functional Equation problem
106830
are $f(f(x))=f(x)$ and $f(x)=x$ equivalent?
17175
Problem in solving functional equation $f(x^2 + yf(x)) = xf(x+y)$
6680
Solve for all possible functions f: $|f(x)-f(y)|=2|x-y|$.
136475
d'Alembert-like functional equation: $f(x+y)+g(x-y)=\lambda f(x)g(y)$
98255
Find $f(x)$ such that $f(f(x)) = x^2 - 2$
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)
48652
Solve the functional equation $2f(x)=f(ax)$ for some $a$.
13042
Finding a function from the given functional equation .
144859
Finding parameters for $f(x) = x^2 + 2(m − a)x + 3am −2 = 0$ that satisfy a condition.
28286
About finding the function such that $f(xy)=f(x)f(y)-f(x+y)+1$
156778
Finding functions satisfying $f(f(x))+f(x)+x=0$
64339
Find $f$ where $f'(x) = f(1+x)$
129599
Functional Equation: Find all functions $f: \mathbb{R} \rightarrow \mathbb{R}$ such that $(x+y)(f(x)-f(y))=(x-y)f(x+y)$
74100
How do you solve $f'(x) = f(f(x))$?