Question 56
Let $x$, $y$, $z$ be non-negative real numbers satisfying $x + y + z = x y z$. Prove that
$$
2\left(x^{2} + y^{2} + z^{2}\right) \geq 3(x + y + z)
$$
and determine when equality occurs.
$$
2\left(x^{2} + y^{2} + z^{2}\right) \geq 3(x + y + z)
$$
and determine when equality occurs.