Sketch Nyquist plot for each of the following GH functions. Determine whether or not each system is stable using Nyquist plot.

(a) \(G_{1}(s) H_{1}(s)=\frac{\left(s^{2}+5ight)}{s^{2}\left(s^{2}+4 s+8ight)}\)

(b) \(\mathrm{G}_{2}(s) \mathrm{H}_{2}(s)=\frac{1}{(s+2)\left(s^{2}+4ight)}\)