(3) If the equation $x^{3}-3 x^{2}-9 x=a$ has exactly two distinct real roots in the interval $[-2,3]$, then the range of the real number $a$ is $\qquad$ .
(3) $[-2,5)$ Hint: Let $f(x)=x^{3}-3 x^{2}-9 x$, then
$$
f^{\prime}(x)=3 x^{2}-6 x-9=3(x+1)(x-3) .
$$

It can be seen that $f(x)$ is an increasing function on the interval $[-2,-1]$, and a decreasing function on $[-1,3]$.

Also, $f(-2)=-2, f(-1)=5, f(3)=-27$, so, combining the graph of the function, it is known that when $-2 \leqslant a<5$, the equation $x^{3}-3 x^{2}-9 x=a$ has exactly two distinct real roots in the interval $[-2,3]$.