None of the poles of a linear control system lie in the right half of $$s$$-plane. For a bounded input, the output of this system

Closed loop stability implies that $$\left[ {1 + G\left( s \right)H\left( s \right)} \right]$$ has only ____________ in the left half of the $$s$$-plane.

The closed loop system , of Figure, is stable if the transfer function $$T\left( s \right) = {{C\left( s \right)} \over {R\left( s \right)}}$$ is stable.

The number of positive real roots of the equation $${s^3} - 2s + 2 = 0$$ is __________.