To solve this problem, we need to find the transfer function of the given system using the Laplace transform and the given relationship between the input \( x(t) \) and output \( y(t) \).
- Transfer Function: The transfer function \( H(s) \) of a system relates the Laplace transform of the output to the Laplace transform of the input. It is defined as:
\[ H(s) = \frac{Y(s)}{X(s)} \]
- Laplace Transform: The Laplace transform of a function \( f(t) \) is given by:
\[ F(s) = \mathcal{L}\{f(t)\} = \int_0^\infty e^{-st} f(t) dt \]
- Step Function \( u(t) \): The step function \( u(t) \) is 0 for \( t < 0 \) and 1 for \( t \geq 0 \). The Laplace transform of \( u(t - a) \) is:
\[ \mathcal{L}\{u(t - a)\} = \frac{e^{-as}}{s} \]
The equation relating the input and output is:
\[ \frac{dy(t)}{dt} + y(t) = 3x(t - 3)u(t - 3) \]
Taking the Laplace transform of both sides:
\[ sY(s) + Y(s) = 3X(s)e^{-3s} \]
Rearranging to find the transfer function:
\[ Y(s)\left(s + 1\right) = 3X(s)e^{-3s} \]
\[ H(s) = \frac{Y(s)}{X(s)} = \frac{3e^{-3s}}{s + 1} \]
The transfer function of the system is \( \frac{3e^{-3s}}{s+1} \).
What is the voltage across the inductor at $t=0$? (Circuit diagram provided: A 60V voltage source in series with a switch that closes at $t=0$, a 30 ohm resistor, and a 15H inductor.) 
The overall impulse response of the system shown in figure is given by (Block diagram provided: Input $X(n)$ splits. One path goes to $h_1[n]$, another to $h_2[n]$. The outputs of $h_1[n]$ and $h_2[n]$ are subtracted. This result is convolved with $h_3[n]$. Separately, $X(n)$ also goes to $h_5[n]$. The output of $h_3[n]$ and $h_5[n]$ are subtracted. This result is convolved with $h_4[n]$ to produce $y(n)$.) 
Which of the following statements is correct?
[I.] All periodic signals are energy signals while aperiodic signals are power signals
[II.] Periodic signals have finite and non-zero average power
[III.] Both periodic and aperiodic signals have infinite power and energy
[IV.] All periodic signals are power signals while aperiodic signals are energy signals