9. The odd function $f(x)$ is increasing on the interval $[3,7]$, and the maximum value on the interval $[3,6]$ is 8, and the minimum value is -1, then $2 f(-6)+f(-3)=$ $\qquad$ .
9. $-15 \quad f(6)=8, f(3)=-1, f(-6)=-8, f(-3)=1$.