9. Given a quadratic equation with real coefficients $a x^{2}+2 b x$ $+c=0$ has two real roots $x_{1} 、 x_{2}$. If $a>b>c$, and $a$ $+b+c=0$, then $d=\left|x_{1}-x_{2}\right|$ the range of values is $\qquad$
9. $\sqrt{3}<d<2 \sqrt{3}$