determine the equation of the midline of the following graph.

Explanation:

Step1: Identify highest and lowest y - values

The highest y - value of the wave is $y=- 2$ and the lowest y - value is $y=-4$.

Step2: Calculate mid - value

The mid - value (midline) of two numbers $a$ and $b$ is given by $\frac{a + b}{2}$. Here $a=-2$ and $b = - 4$, so $\frac{-2+( - 4)}{2}=\frac{-2 - 4}{2}=\frac{-6}{2}=-3$.

Answer:

$y=-3$