Solving $f(x/2)^2=f(x)$
34074
Nonlinear Functional Equation $f(x)^{2}=f\left(\frac x a\right)$
68774
Proving that $f(x)$ is less than or equal to $1+\pi/4$
66772
$f(f(x)f(y))+f(x+y)=f(xy)$
19474
Find all solutions to the functional equation $f(x) +f(x+y)=y+2 $
142682
Find $f(x)$ where $ f(x)+f\left(\frac{1-x}x\right)=x$
64339
Find $f$ where $f'(x) = f(1+x)$
64448
Find a quadratic equation with root $x_1^2$ and $x_2^2$
31698
$f(m^2 + f(n)) = f(m)^2 + n$ for all natural numbers
47212
Solving functional equation
127796
Degree of field extension $F(x) / F(x^2 + 1 / x^2)$
147325
Proving that if $f(x)=x$ has no real solution then $f(f(x))=x$ has no real solution either
117353
Polynomial equation $f(x)f(2x^2)=f(2x^3+x)$
9270
Differentiable function, with $f'(x)=[f(x)]^2$
23465
When $f(x+1)-f(x)=f'(x)$, what are the solutions for $f(x)$?
17175
Problem in solving functional equation $f(x^2 + yf(x)) = xf(x+y)$
144090
How to solve the functional equation $f\left(x^2+f(y)\right)=y+f(x)^2$
105999
An application of derivatives problem- to show that $f(x+2)-f(x)>2$ for $f(x)=x\cos(1/x)$