The Laplace transform of $f(t) = 2t + 6$ is $\frac{1}{s}+\frac{2}{s^2}$ $\frac{3}{s}-\frac{6}{s^2}$ $\frac{6}{s}+\frac{2}{s^2}$ $-\frac{6}{s}+\frac{2}{s^2}$

The Laplace transform $F(s)$ of the function $f(t) = \cos (at)$, where $a$ is constant, _________ $\dfrac{s^2}{s^2+a^2} \\$ $\dfrac{a}{s^2+a^2} \\$ $\dfrac{s}{s^2+a^2} \\$ $\dfrac{s}{s^2-a^2} $

$\dfrac{d^2y}{dx^2}-y=0$. The conditions for this second order homogeneous differential equation are $y(0)=1$ and $\dfrac{dy}{dx}=3$ at $x=0$. The value of $y$ when $x = 2$ is __________

All professors are researchers. Some scientists are professors. Which of the given conclusions is logically valid and is inferred from the above arguments: All scientists are researchers All professors are scientists Some researchers are scientists No conclusion follows