Answer
$y=3cos(\frac{\pi}{6}x)$
Work Step by Step
1. The given curve resembles a cosine function with a general form $y=A\ cos(kx)$
2. We can find the amplitude$=3$, period$=6-(-6)=12$.
3. We have $A=3$, $\frac{2\pi}{k}=12$, thus $k=\frac{\pi}{6}$.
4. Thus we have $y=3cos(\frac{\pi}{6}x)$
