Answer:
![A(w) = w^2 + 5w - \frac{1}{8}\pi w^2](https://tex.z-dn.net/?f=%20A%28w%29%20%3D%20w%5E2%20%2B%205w%20-%20%5Cfrac%7B1%7D%7B8%7D%5Cpi%20w%5E2%20)
Step-by-step explanation:
A = the area of the region outside the semicircle but inside the rectangle
w = the width of the rectangle or diameter of the semicircle
Since "A" is determined by "w", therefore, "A" is a function of "w" = A(w).
A(w) = (area of rectangle) - (area of semicircle)
![A(w) = (l*w) - (\frac{1}{2} \pi r^2)](https://tex.z-dn.net/?f=%20A%28w%29%20%3D%20%28l%2Aw%29%20-%20%28%5Cfrac%7B1%7D%7B2%7D%20%5Cpi%20r%5E2%29%20)
Where,
lenght of rectangle (l) = w + 5
width of rectangle (w) = w
r = ½*w = ![\frac{w}{2}](https://tex.z-dn.net/?f=%20%5Cfrac%7Bw%7D%7B2%7D%20)
Plug in the values:
![A(w) = ((w + 5)*w) - (\frac{1}{2} \pi (\frac{w}{2})^2)](https://tex.z-dn.net/?f=%20A%28w%29%20%3D%20%28%28w%20%2B%205%29%2Aw%29%20-%20%28%5Cfrac%7B1%7D%7B2%7D%20%5Cpi%20%28%5Cfrac%7Bw%7D%7B2%7D%29%5E2%29%20)
![A(w) = ((w + 5)*w) - (\frac{1}{2} \pi (\frac{w}{2})^2)](https://tex.z-dn.net/?f=%20A%28w%29%20%3D%20%28%28w%20%2B%205%29%2Aw%29%20-%20%28%5Cfrac%7B1%7D%7B2%7D%20%5Cpi%20%28%5Cfrac%7Bw%7D%7B2%7D%29%5E2%29%20)
Simplify
![A(w) = (w^2 + 5w) - (\frac{1}{2} \pi (\frac{w^2}{4})](https://tex.z-dn.net/?f=%20A%28w%29%20%3D%20%28w%5E2%20%2B%205w%29%20-%20%28%5Cfrac%7B1%7D%7B2%7D%20%5Cpi%20%28%5Cfrac%7Bw%5E2%7D%7B4%7D%29%20)
![A(w) = w^2 + 5w - \frac{1}{2}*\pi*\frac{w^2}{4}* \pi](https://tex.z-dn.net/?f=%20A%28w%29%20%3D%20w%5E2%20%2B%205w%20-%20%5Cfrac%7B1%7D%7B2%7D%2A%5Cpi%2A%5Cfrac%7Bw%5E2%7D%7B4%7D%2A%20%5Cpi%20)
![A(w) = w^2 + 5w - \frac{1*\pi*w^2}{2*4}](https://tex.z-dn.net/?f=%20A%28w%29%20%3D%20w%5E2%20%2B%205w%20-%20%5Cfrac%7B1%2A%5Cpi%2Aw%5E2%7D%7B2%2A4%7D%20)
![A(w) = w^2 + 5w - \frac{1*\pi w^2}{8}](https://tex.z-dn.net/?f=%20A%28w%29%20%3D%20w%5E2%20%2B%205w%20-%20%5Cfrac%7B1%2A%5Cpi%20w%5E2%7D%7B8%7D%20)
![A(w) = w^2 + 5w - \frac{1}{8}\pi w^2](https://tex.z-dn.net/?f=%20A%28w%29%20%3D%20w%5E2%20%2B%205w%20-%20%5Cfrac%7B1%7D%7B8%7D%5Cpi%20w%5E2%20)