The least value of the function $f(x)=|x-a|+|x-b|+|x-c|+|x-d|$
7740
The median minimizes the sum of absolute deviations (the $ {\ell}_{1} $ norm)
33247
Does $f(0)=0$ and $\left|f^\prime(x)\right|\leq\left|f(x)\right|$ imply $f(x)=0$?
65827
When $\min_{x \in X,y \in Y} f(x,y) = \min_{x \in X} \min_{y \in Y} f(x,y)$?
53536
Maximum value of $f(x) = \cos x \left( \sin x + \sqrt {\sin^2x +\sin^2a}\right)$
41226
Find $f:f(xf(x)+f(y))=f(x)^2+y$
53024
$f(x)f(1/x)=f(x)+f(1/x)$
136655
Find the range of the given function $f$
40779
What is the smallest possible value of $\lfloor (a+b+c)/d\rfloor+\lfloor (a+b+d)/c\rfloor+\lfloor (a+d+c)/b\rfloor+\lfloor (d+b+c)/a\rfloor$?
21986
What is the minimum value of $(1 + a_1)(1 + a_2). . .(1 + a_n)$?
126259
Minimum of a function on an open interval
132093
Solve $f(f(x))=f(x)$
17343
Function on $[a,b]$ that satisfies a Hölder condition of order $\alpha > 1 $ is constant
13220
find the minimum value of $\frac{a}{b}+\frac{b}{c}+\frac{c}{a}$
155493
Minimum value of the expression given below.
88271
Prove the exsistence of 3 zero points of a function
28286
About finding the function such that $f(xy)=f(x)f(y)-f(x+y)+1$
156778
Finding functions satisfying $f(f(x))+f(x)+x=0$