Is $f(x) > 0$ for all $x>0$?
64836
Functions that are always less than their derivatives
82371
$f$ is an entire function with Im $f\geq 0$
47026
if $f^{(n)}(x_0),g^{(n)}(x_0)$ exist and $\lim_{x\to x_0} \dfrac{f(x)-g(x)}{(x-x_0)^n}=0$ then $f^{(r)}(x_0)=g^{(r)}(x_0 )$ for all $0\leq r\leq n.$
59063
$f(f(x))=f(x)$ question
104263
How to show that $f'(x)<2f(x)$
84785
Is $f(x)=x+\frac{x}{x+1}$ uniformly continuous on $(0,\infty)$
151519
If $f(f(x))=x^2-x+1$, what is $f(0)$?
40070
Is there a real-valued function $f$ such that $f(f(x)) = -x$?
119060
What can you say about a continuous function that is zero at all integer values?
88311
Linear functional f(v)=0 imply v=0
30860
Prove that $f(x)=0$ in $[-1,1]$.
8836
If $f$ is continuous on $[a , b]$ and $\int_a^b f(x) p(x)dx = 0$ then $f = 0$
61500
If f is continous and exist real numbers show that $f(x)=0$
28011
Does there exists an entire function such that for each $|z|>C$ for some constant $C$, $|f(z)|=|z|+1$?
58901
Why is every such function constant: $f(x)=f(x^2)$ for $x \in [0,1]$?
111485
Let $f(x)$ be continuous on [$0,1$] to $f(x)=0$ for each $x\in[0,1]$
2717
Help proving existence of an specific $x_0$ for which $f''(x_0)=0$