C9: Thay $x=-\frac{1}{3}$ vào L, ta được:
$5.\left ( -\frac{1}{3} \right ).\left ( -\frac{1}{3}-1 \right )\left ( 2.\left ( -\frac{1}{3}+3 \right ) \right )-10.\left ( -\frac{1}{3} \right ).\left ( \left ( -\frac{1}{3} \right )^{2}-4.\left ( -\frac{1}{3} +5\right ) \right )-\left ( -\frac{1}{3}-1 \right ).\left ( -\frac{1}{3}-4 \right )$
$=5.\left ( -\frac{1}{3} \right ).\left ( -\frac{4}{3} \right ).\left ( -\frac{2}{3}+3 \right )-10.\left ( -\frac{1}{3} \right ).\left ( \frac{1}{9}+\frac{4}{3}+5 \right )-\left ( -\frac{4}{3} \right ).\left ( -\frac{13}{3} \right )$
$=5.\left ( -\frac{1}{3} \right ).\left ( -\frac{4}{3} \right ).\frac{7}{3}-10.\left ( -\frac{1}{3} \right ).\frac{58}{9}+\frac{4}{3}.\left ( -\frac{13}{3} \right )$
$=\frac{140}{27}+\frac{580}{27}-\frac{52}{9}=\frac{188}{9}$
