(There are an infinite number of answers)
Since the function is positive a 0, choose the cosine function y = y=Acos(B(x−D))+C
Find the midline at y = -1. This means our A(mplitude) is 3 because Max = 2 and min = -4
The function completes one cycle as x varies from 0 to 4, so our period is 4
In our general form, the period = |2pi/B| so B = pi/2
The vertical shift is -1, to bring the x-axis down to the midline; C = -1
There is no phase shift; D = 0
We write y = 3cos(pi*x/2) -1