4. For what values of $a$ is the system $\left\{\begin{array}{c}10 x^{2}+x-a-11=0 \\ 4 x^{2}+(a+4) x-3 a-8=0\end{array} \mathrm{c}\right.$ consistent? Solve the system for all permissible $a$.
Answer: 1) the system is consistent for $a=0,-2,54$;

2) when $a=0$, $x=1$; when $a=-2$, $x=-1$; when $a=54$, $x=\frac{5}{2}$.