Find all $f: \mathbb{Q} \rightarrow \mathbb{R}$ such that $f(x+y) = f(x)+f(y)$
103251
Solution(s) to $f(x + y) = f(x) + f(y)$ (and miscellaneous questions...)
14495
I need to find all functions $f:\mathbb R \rightarrow \mathbb R$ which are continuous and satisfy $f(x+y)=f(x)+f(y)$
78698
Prove if $f$ has a right inverse function: $f\circ g=id_x$ $\iff$ $f$ is onto $Y$
156778
Finding functions satisfying $f(f(x))+f(x)+x=0$
153942
Solution of functional equation $f(x+y)=f(x)+f(y)+y\sqrt{f(x)}$
32856
Functional equations $f(x+y)= f(x) + f(y)$ and $f(xy)= f(x)f(y)$
158182
Let $R = \mathbb{Z} + x\mathbb{Q}[x]$. Find all the irreducibles in $R$.
9957
Prove if $f:[a,b] \rightarrow \mathbb{R}$ is integrable, then so is $|f|$ and $\left|\int_{a}^{b}f(x)dx\right| \leq \int_{a}^{b}|f(x)|dx$
11453
Find a real function $f:\mathbb{R}\to\mathbb{R}$ such that $f(f(x)) = -x$?
31732
If the function $f$ satisfies the equation $f(xf(y)+x)=xy+f(x)$, find $f$
33330
Continuous Functions from $\mathbb{R}$ to $\mathbb{Q}$
11828
continuous functions on $\mathbb R$ such that $g(x+y)=g(x)g(y)$
131586
Hard functional equation: $ f \big ( x y + f ( x ) \big) = f \big( f ( x ) f ( y ) \big) + x $
155165
Prove that $\mathbb F_8=\mathbb F_2[X]/(X^3+X+1)$
143354
Prove that there exists $c\in\mathbb{R}$ such that $f'(c)=f(c)$
44293
Functions satisfying $f\left( f(x)^2+f(y) \right)=xf(x)+y$
66772
$f(f(x)f(y))+f(x+y)=f(xy)$