Chapter 12: Problem 3
Find the first partial derivatives of the function. \(f(x, y)=2 x+3 y+5\)
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Chapter 12: Problem 3
Find the first partial derivatives of the function. \(f(x, y)=2 x+3 y+5\)
These are the key concepts you need to understand to accurately answer the question.
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Find the first partial derivatives of the function. \(f(s, t)=\left(s^{2}-s t+t^{2}\right)^{3}\)
The monthly profit (in dollars) of Bond and Barker Department Store depends on the level of inventory \(x\) (in thousands of dollars) and the floor space \(y\) (in thousands of square feet) available for display of the merchandise, as given by the equation $$\begin{aligned}P(x, y)=&-0.02 x^{2}-15 y^{2}+x y \\ &+39 x+25 y-20,000\end{aligned}$$ Compute \(\partial P / \partial x\) and \(\partial P / \partial y\) when \(x=4000\) and \(y=150\). Interpret your results. Repeat with \(x=5000\) and \(y=150\).
The total daily revenue (in dollars) that Weston Publishing realizes in publishing and selling its English-language dictionaries is given by $$\begin{aligned}R(x, y)=&-0.005 x^{2}-0.003 y^{2}-0.002 x y \\\&+20 x+15 y\end{aligned}$$ where \(x\) denotes the number of deluxe copies and \(y\) denotes the number of standard copies published and sold daily. The total daily cost of publishing these dictionaries is given by $$C(x, y)=6 x+3 y+200$$ dollars. Determine how many deluxe copies and how many standard copies Weston should publish each day to maximize its profits. What is the maximum profit realizable?
Let \(f(x, y)=9-x^{2}+x y-2 y^{2}\). a. Find \(f_{x}(1,2)\) and \(f_{y}(1,2)\). b. Interpret the numbers in part (a) as slopes. c. Interpret the numbers in part (a) as rates of change.
The monthly payment that amortizes a loan of \(A\) dollars in \(t\) yr when the interest rate is \(r\) per year, compounded monthly, is given by $$P=f(A, r, t)=\frac{A r}{12\left[1-\left(1+\frac{r}{12}\right)^{-12 t}\right]}$$ a. What is the monthly payment for a home mortgage of $$\$ 300,000$$ that will be amortized over \(30 \mathrm{yr}\) with an interest rate of \(6% /\) year? An interest rate of \(8 \% /\) year? b. Find the monthly payment for a home mortgage of $$\$ 300,000$$ that will be amortized over 20 yr with an interest rate of \(8 \% /\) year.
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