$x(t=1 s)=A \sin \left(\frac{2 \pi}{T} t\right)=A \sin \left(\frac{2 \pi}{8}\right)=A \sin \left(\frac{\pi}{4}\right)=\frac{A}{\sqrt{2}}$
$x(t=2 s)=A \sin \left(\frac{2 \pi}{T} t\right)=A \sin \left(\frac{2 \pi}{8} \times 2\right)=A \sin \left(\frac{\pi}{2}\right)=A$
And the required ratio is$:$
$\frac{x(t=1 s)}{x(t=2 s)-x(t=1 s)}=\frac{\frac{A}{\sqrt{2}}}{A-\frac{A}{\sqrt{2}}}=\frac{1}{\sqrt{2}-1}=\sqrt{2}+1$


$(A)$ the speed of the particle when it returns to its equilibrium position is $u_0$.
$(B)$ the time at which the particle passes through the equilibrium position for the first time is $t=\pi \sqrt{\frac{ m }{ k }}$.
$(C)$ the time at which the maximum compression of the spring occurs is $t =\frac{4 \pi}{3} \sqrt{\frac{ m }{ k }}$.
$(D)$ the time at which the particle passes througout the equilibrium position for the second time is $t=\frac{5 \pi}{3} \sqrt{\frac{ m }{ k }}$.
