9 Given that $y=(x-16)(x-14)(x+14)(x+16)$, find the minimum value of $y$.
(A) -896
(B) -897
(C) -898
(D) -899
(E) $\quad-900$
9 Answer: (E)
$$
y=\left(x^{2}-16^{2}\right)\left(x^{2}-14^{2}\right)=x^{4}-452 x^{2}+50176=\left(x^{2}-226\right)^{2}-900
$$

So minimum value of $y=-900$.