$f$ Concave function such as $f(0)=0$
7825
If $f$ is a concave function and $f(0) \geq 0$ then $f(a+b) \leq f(a) + f(b)$ for all $a,b >0$
149328
A function such that $f:\mathbb C \to \mathbb C$ such that $f(z)f(iz)=z^2$ satisfies $f(z)+f(-z)=0$.(MADHAVA-2020)
88311
Linear functional f(v)=0 imply v=0
20614
Example of a function such that $\varphi\left(\frac{x+y}{2}\right)\leq \frac{\varphi(x)+\varphi(y)}{2}$ but $\varphi$ is not convex
39090
Finding functions such that $f(g(x)) = f(x)g(x)$
135867
$f(x)=x^3$ is convex nor concave without to derivate
150727
Characterization convex function.
113888
Behavior of derivative near the zero of a function.
11453
Find a real function $f:\mathbb{R}\to\mathbb{R}$ such that $f(f(x)) = -x$?
8963
Function that is both midpoint convex and concave
42901
Find the values of $\alpha$ and $\beta$ for which the function $f$ is of bounded variation on $[0,1]$?
40070
Is there a real-valued function $f$ such that $f(f(x)) = -x$?
17343
Function on $[a,b]$ that satisfies a Hölder condition of order $\alpha > 1 $ is constant
23186
$f: \mathbb{R^2} \to \mathbb{R}$ a $C^\infty$ function such that $f(x,0)=f(0,y)=0$ then exists $g$ such that $f(x,y)=xy\, g(x,y)$
112923
Let $f:\mathbb{R}\longrightarrow \mathbb{R}$ a differentiable function such that $f'(x)=0$ for all $x\in\mathbb{Q}$
72769
How find this function $xf(x^2)=f(x),x>0$
123249
An analytic function $f$ on $|z|<1$ with $\sup_{|z|<1} |f(z)|=1$ and $|f(0)|=\frac{1}{2}$ has no zeros in $|z|<\frac{1}{2}$