What is the midline equation of the function h(x)=-4\sin\left(x-\dfrac{\pi}{4}\right)h(x)=−4sin(x−
4
π
​
)h, left parenthesis, x, right parenthesis, equals, minus, 4, sine, left parenthesis, x, minus, start fraction, pi, divided by, 4, end fraction, right parenthesis?