Answer
$y=-7sin(\frac{\pi}{4}x)$
Work Step by Step
1. The given graph resembles to $y=-sin(x)$, with a general form $y=-A\ sin(\omega x)$,
2. We can find the amplitude$A=7$, period$=8$, phase shift$=0$.
3. We have $\frac{2\pi}{\omega}=8$, thus $\omega=\frac{\pi}{4}$
4. Thus we have $y=-7sin(\frac{\pi}{4}x)$
