Question 38
Find all functions $f:\mathbb R^+\to\mathbb R$, where $\mathbb R^+=(0,+\infty)$, such that for every $x,y\in\mathbb R^+$,
$$f\left(\sqrt{\frac{x^2+xy+y^2}{2012}}\right)=\frac{f(x)-f(y)}2.$$
$$f\left(\sqrt{\frac{x^2+xy+y^2}{2012}}\right)=\frac{f(x)-f(y)}2.$$