Q$2(30$ Points$)$: Consider a closed$-$loop control system with the characteristic equation

$()=1+()$

Using the Nyquist Stability Criterion to determine the stability of the closed$-$loop system.

$10$

$1.()=$

$(+1)(+2)(+3)$

$2(4)(0\mathrm{.}5)$

$2.()=$

$(1)(+2)(3)(0\mathrm{.}1)$