Chapter 10: Problem 10
Evaluate each function at the given point. \(f(x, y, z)=x^{2}-3 y+z\) at \((3,-1,1)\)
Short Answer
Step by step solution
Key Concepts
These are the key concepts you need to understand to accurately answer the question.
/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none}
Learning Materials
Features
Discover
Chapter 10: Problem 10
Evaluate each function at the given point. \(f(x, y, z)=x^{2}-3 y+z\) at \((3,-1,1)\)
These are the key concepts you need to understand to accurately answer the question.
All the tools & learning materials you need for study success - in one app.
Get started for free
Parasites live by stealing resources from hosts. When parasites reproduce their offspring must find new hosts. However, if a potential host is already infected by parasites, then new parasites will not be able to infect it. This leads to interference between parasites, and we will build a model for these effects in this Problem. We assume that \(N\) is the number of hosts in a given area, and \(P\) is the number of parasites. A frequently used model for host- parasite interactions is the Nicholson-Bailey model (see Nicholson and Bailey, 1935 ), in which it is assumed that the number of parasitized hosts, denoted by \(N_{a}\), is given by $$N_{a}=N\left[1-e^{-b P}\right]$$ where \(b\) is the searching efficiency. (a) Let's treat \(N\) and \(P\) as independent variables and \(N_{n}\) as a function of \(N\) and \(P .\) By calculating the appropriate partial derivatives investigate how: (i) an increase in the number of hosts \(N\) affects the number of parasitized hosts \(N_{a}(N, P)\) (ii) an increase in the number of parasites affects the number of parasitized hosts \(N_{a}(N, P)\) (b) Show that $$b=\frac{1}{P} \ln \frac{N}{N-N_{a}}$$ by solving \((10.6)\) for \(b\). (c) Consider $$b=f\left(P, N, N_{\alpha}\right)=\frac{1}{P} \ln \frac{N}{N-N_{a}}$$ That is, we regard searching efficiency as a function of \(P, N\), and \(N_{n} .\) How is the searching efficiency \(b\) affected when the, number of parasites increases?
Find the range of each function \(f(x, y)\), when defined on the specified domain \(D\). \(f(x, y)=\frac{x}{y} ; D=\\{(x, y): 0 \leq x \leq 1,1 \leq y \leq 2\\}\)
Find the range of each function \(f(x, y)\), when defined on the specified domain \(D\). \(f(x, y)=x-y^{2} ; D=\\{(x, y):-1 \leq x \leq 1,1 \leq y \leq 2\\}\)
At the beginning of this chapter we introduced the heat index as a way of calculating how temperature and humidity affect the apparent temperature. The equation for the heat index is: \(\begin{aligned} H(T, R)=&-42.38+2.049 T+10.14 R-6.838 \times 10^{-3} T^{2} \\\ &-0.2248 T R-5.482 \times 10^{-2} R^{2}+1.229 \times 10^{-3} T^{2} R \\\ &+8.528 \times 10^{-4} T R^{2}-1.99 \times 10^{-6} T^{2} R^{2} \end{aligned}\) where \(T\) is the actual air temperature (in \({ }^{\circ} \mathrm{F}\) ) and \(R\) is the relative humidity (in \%). Using nine evenly spaced points and five colors, make a heat map for the heat index for the domain \(D=\\{(T, R):\) \(80 \leq T \leq 100,40 \leq R \leq 60]\). (You will find it easiest to calculate the heat index, \(H\), if you program the formula for the heat index into a graphing calculator.)
Determine the equation of the level curves \(f(x, y)=c\) and sketch the level curves for the specified values of \(c\). \(f(x, y)=x^{2}-y^{2} ; c=0,1,-1\)
What do you think about this solution?
We value your feedback to improve our textbook solutions.