3. What is $\sqrt{2004 \cdot 2002 \cdot 1998 \cdot 1996+36}$ ?
II/3. Let $a=2000$. Then the sought value is

$$
\begin{aligned}
\sqrt{(a+4)(a+2)(a-2)(a-4)+36} & =\sqrt{\left(a^{2}-16\right)\left(a^{2}-4\right)+36}= \\
& =\sqrt{a^{4}-20 a^{2}+64+36}=\sqrt{\left(a^{2}-10\right)^{2}}= \\
& =\left|a^{2}-10\right|
\end{aligned}
$$

If we consider that $a=2000$, we get the value $2000^{2}-10=4000000-10=3999990$.

The transformation into the difference of squares $\left(a^{2}-16\right)\left(a^{2}-4\right)$, can also be done without introducing $a=2000$: 3 points. Writing the perfect square $\left(a^{2}-10\right)^{2}$: 3 points. The result 3999990: 1 point.

If the contestant correctly multiplies the expression under the root but does not take the root: 2 points. If the contestant incorrectly multiplies the expression under the root: 0 points. The use of a calculator is, of course, not allowed.