Question 74
Find all functions $f : \mathbb{R}^+ \to \mathbb{R}^+$ such that for all positive real numbers $x$ and $y$, we have
$$
f(f(f(xy)) + x^2) = f(y)(f(x) - f(x + y))
$$
*Note. By $\mathbb{R}^+$, we mean the set of positive real numbers.*
$$
f(f(f(xy)) + x^2) = f(y)(f(x) - f(x + y))
$$
*Note. By $\mathbb{R}^+$, we mean the set of positive real numbers.*