Answer:
Part A)
![\displaystyle \frac{dy}{dx}=-\frac{3}{7}P^\frac{10}{7}x^{-\frac{10}{7}}](https://tex.z-dn.net/?f=%5Cdisplaystyle%20%5Cfrac%7Bdy%7D%7Bdx%7D%3D-%5Cfrac%7B3%7D%7B7%7DP%5E%5Cfrac%7B10%7D%7B7%7Dx%5E%7B-%5Cfrac%7B10%7D%7B7%7D%7D)
Part B)
The daily operating cost decreases by about $143 per extra worker.
Step-by-step explanation:
We are given the equation:
![\displaystyle P=x^{\frac{3}{10}}y^{\frac{7}{10}}](https://tex.z-dn.net/?f=%5Cdisplaystyle%20P%3Dx%5E%7B%5Cfrac%7B3%7D%7B10%7D%7Dy%5E%7B%5Cfrac%7B7%7D%7B10%7D%7D)
Where <em>P</em> is the number of eggs laid, <em>x</em> is the number of workers, and <em>y</em> is the daily operating budget (assuming in US dollars $).
A)
We want to find dy/dx.
So, let’s find our equation in terms of <em>x</em>. We can raise both sides to 10/7. Hence:
![\displaystyle P^\frac{10}{7}=\Big(x^\frac{3}{10}y^\frac{7}{10}\Big)^\frac{10}{7}](https://tex.z-dn.net/?f=%5Cdisplaystyle%20P%5E%5Cfrac%7B10%7D%7B7%7D%3D%5CBig%28x%5E%5Cfrac%7B3%7D%7B10%7Dy%5E%5Cfrac%7B7%7D%7B10%7D%5CBig%29%5E%5Cfrac%7B10%7D%7B7%7D)
Simplify:
![\displaystyle P^\frac{10}{7}=x^\frac{3}{7}y](https://tex.z-dn.net/?f=%5Cdisplaystyle%20P%5E%5Cfrac%7B10%7D%7B7%7D%3Dx%5E%5Cfrac%7B3%7D%7B7%7Dy)
Divide both sides by<em> </em>the <em>x</em> term to acquire:
![\displaystyle y=P^\frac{10}{7}x^{-\frac{3}{7}}](https://tex.z-dn.net/?f=%5Cdisplaystyle%20y%3DP%5E%5Cfrac%7B10%7D%7B7%7Dx%5E%7B-%5Cfrac%7B3%7D%7B7%7D%7D)
Take the derivative of both sides with respect to <em>x: </em>
![\displaystyle \frac{dy}{dx}=\frac{d}{dx}\Big[P^\frac{10}{7}x^{-\frac{3}{7}}\Big]](https://tex.z-dn.net/?f=%5Cdisplaystyle%20%5Cfrac%7Bdy%7D%7Bdx%7D%3D%5Cfrac%7Bd%7D%7Bdx%7D%5CBig%5BP%5E%5Cfrac%7B10%7D%7B7%7Dx%5E%7B-%5Cfrac%7B3%7D%7B7%7D%7D%5CBig%5D)
Apply power rule. Note that P is simply a constant. Hence:
![\displaystyle \frac{dy}{dx}=P^\frac{10}{7}(-\frac{3}{7})(x^{-\frac{10}{7}})](https://tex.z-dn.net/?f=%5Cdisplaystyle%20%5Cfrac%7Bdy%7D%7Bdx%7D%3DP%5E%5Cfrac%7B10%7D%7B7%7D%28-%5Cfrac%7B3%7D%7B7%7D%29%28x%5E%7B-%5Cfrac%7B10%7D%7B7%7D%7D%29)
Simplify. Hence, our derivative is:
![\displaystyle \frac{dy}{dx}=-\frac{3}{7}P^\frac{10}{7}x^{-\frac{10}{7}}](https://tex.z-dn.net/?f=%5Cdisplaystyle%20%5Cfrac%7Bdy%7D%7Bdx%7D%3D-%5Cfrac%7B3%7D%7B7%7DP%5E%5Cfrac%7B10%7D%7B7%7Dx%5E%7B-%5Cfrac%7B10%7D%7B7%7D%7D)
Part B)
We want to evaluate the derivative when <em>x</em> is 30 and when <em>y</em> is $10,000.
First, we will need to find <em>P</em>. Our original equations tells us that:
![P=x^{0.3}y^{0.7}](https://tex.z-dn.net/?f=P%3Dx%5E%7B0.3%7Dy%5E%7B0.7%7D)
Hence, at <em>x</em> = 30 and at <em>y</em> = 10,000, <em>P </em>is:
![P=(30)^{0.3}(10000)^{0.7}](https://tex.z-dn.net/?f=P%3D%2830%29%5E%7B0.3%7D%2810000%29%5E%7B0.7%7D)
Therefore, for our derivative, we will have:
Use a calculator. So:
![\displaystyle \frac{dy}{dx}=-\frac{1000}{7}=-142.857142...\approx-143](https://tex.z-dn.net/?f=%5Cdisplaystyle%20%5Cfrac%7Bdy%7D%7Bdx%7D%3D-%5Cfrac%7B1000%7D%7B7%7D%3D-142.857142...%5Capprox-143)
Our derivative is given by dy/dx. So, it represents the change in the daily operating cost over the change in the number of workers.
So, when there are 30 workers with a daily operating cost of $10,000 producing a total of about 1750 eggs, the daily operating cost decreases by about $143 per extra worker.