3. The number of real roots of the equation $x^{2}|x|-5 x|x|+2 x=0$ is $\qquad$.

The equation $x^{2}|x|-5 x|x|+2 x=0$ has $\qquad$ real roots.
3.4 .

From the given, we have $x(x|x|-5|x|+2)=0$.
Thus, $x=0$ or $x|x|-5|x|+2=0$.
(1) When $x>0$, $x^{2}-5 x+2=0$, which has two distinct positive real roots;
(2) When $x<0$, $-x^{2}+5 x+2=0$, which has one negative real root.
Therefore, the original equation has 4 real roots.