Signals and Sys...

A CT signal is given as x(t) = [P + Qe^-bt] u(t) where P and Q we constant. The ROC of Laplace transform of x(t) is

A signal x(t) has the Laplace transform \(X\left( s \right) = \frac{s}{{\left( {{s^2} + 9} \right)}},\;Re\left( s \right) < 0\). The signal x(t) at t = -π/3 ______ 

The Laplace transform of a causal signal y(t) is Y(s) = \(\frac{{s + 4}}{{s + 8}}\). The value of the signal y(t) at t = 0.15 sec is ____

For a system, transfer function \(H\left( s \right) = \frac{{b\left( {s + a} \right)}}{{s + b}}\) & unit step response is y(t). If y(0) = 4 & steady state value of y(t) is 20 then b/a is