Ex$.324.$ Given six closed$-$loop characteristic equations: a$)$ s$^3+9$s$^2+6$s $-4=0$b$)$ s$^3+7$s$^2-5$s $+5=0$ c$)$ s$^3+1$s$^2+2$s $-3=0$d$)$ s$^3-2$s$^2+5$s $+8=0$ e$)$ s$^3+4$s$^2+8$s $=0$f$)$ s$^3+8$s $+7=0$ Determine if each system is not stable, by observation only $($no calculations$).$If so enter $0,$ otherwise enter $1.$ ans:$624$ sammoh$461$group$3$