Question 94
Find all non-constant functions $f: \mathbb{Q}^+ \to \mathbb{Q}^+$ satisfying the equation
$$
f(ab + bc + ca) = f(a)f(b) + f(b)f(c) + f(c)f(a)
$$
for all $a, b, c \in \mathbb{Q}^+$.
$$
f(ab + bc + ca) = f(a)f(b) + f(b)f(c) + f(c)f(a)
$$
for all $a, b, c \in \mathbb{Q}^+$.