/*! 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} Problem 55 Let \(f(x)=x e^{2 x}\) a. Find... [FREE SOLUTION] | 91Ó°ÊÓ

91Ó°ÊÓ

Let \(f(x)=x e^{2 x}\) a. Find the values of \(x\) for which the slope of the curve \(y=f(x)\) is 0. b. Explain the meaning of your answer to part (a) in terms of the graph of \(f\)

Short Answer

Expert verified
Answer: The slope of the curve \(y = x e^{2x}\) becomes 0 at \(x = -\frac{1}{2}\). This means that there is either a local maximum or minimum or a point of inflection of the graph of \(f(x) = x e^{2x}\) at this point.

Step by step solution

01

a. Finding the values of \(x\) for which the slope of the curve is 0.

First, we need to find the derivative of the given function, \(f(x)=x e^{2x}\). To do this, we will use the product rule, which states that if \(u\) and \(v\) are functions of \(x\), then \((u \cdot v)' = u' \cdot v + u \cdot v'\). Here, we have \(u=x\) and \(v=e^{2x}\). Therefore, \(u'=1\) and \(v'=2 e^{2x}\) (using the chain rule for \(v'\)). Applying the product rule, we get: \(f'(x) = u' \cdot v + u \cdot v'\) \(f'(x) = (1) \cdot e^{2x} + x \cdot 2e^{2x}\) \(f'(x) = e^{2x}(1+2x)\) Now, we are asked to find the values of \(x\) for which the slope of the curve \(y=f(x)\) is 0. In other words, we need to find the values of \(x\) for which \(f'(x) = 0\). So, we set \(f'(x)\) to 0 and solve for \(x\): \(0 = e^{2x}(1+2x)\) Now we have two factors: \(e^{2x}\) and \((1+2x)\). Since exponential functions are never 0, \(e^{2x}\) cannot equal 0. Therefore, we set \((1+2x)=0\): \(0 = 1+2x\) \(2x = -1\) \(x = -\frac{1}{2}\) So, the value of \(x\) for which the slope of the curve \(y=f(x)\) is 0 is \(x=-\frac{1}{2}\).
02

b. Explaining the meaning of the answer to part (a) in terms of the graph of \(f\)

In part (a), we found that the slope of the curve \(y=f(x)\) is 0 at \(x=-\frac{1}{2}\). The slope of a curve at a certain point represents the steepness of the tangent to that point. When the slope is 0, it means the tangent to the curve is horizontal. This usually happens at points where the function is at a maximum or minimum (local or global) or a point of inflection. In this case, having a slope of 0 at \(x=-\frac{1}{2}\) means that there is either a local maximum or minimum or a point of inflection of the graph of \(f(x) = x e^{2x}\) at that point.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!

Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Product Rule
When finding the derivative of a function composed of two differentiable functions multiplied together, the product rule is an essential tool.
The product rule states that for two functions, say \( u(x) \) and \( v(x) \), the derivative of their product \( u(x) \cdot v(x) \) is given by:
\[ (u \cdot v)' = u' \cdot v + u \cdot v' \].
This means that you take the derivative of the first function \( u \), multiply it by the second function \( v \), and add the product of the first function \( u \) and the derivative of the second function \( v \).In the given exercise, the function \( f(x) = x e^{2x} \) can be broken down into \( u = x \) and \( v = e^{2x} \).
  • The derivative \( u' \) is straightforward; \( u' = 1 \).
  • For \( v' \), you need to apply the chain rule, which gives \( v' = 2e^{2x} \).
Applying the product rule yields the derivative as \( f'(x) = e^{2x}(1 + 2x) \). This methodology is key to solving the problem and finding the slope at any point on the curve.
Understanding how each part contributes to the derivative helps demystify the process.
Chain Rule
Sometimes, functions are composed of other functions, and when differentiating, it's necessary to take into consideration the inner function. That's where the chain rule comes in handy.
The chain rule is used to differentiate composite functions. If you have a function \( h(x) = g(f(x)) \), then the derivative \( h'(x) \) is found by using:
\[ h'(x) = g'(f(x)) \cdot f'(x) \].
This means, differentiate the outer function \( g \) evaluated at \( f(x) \), and then multiply it by the derivative of the inner function \( f \).In the exercise, the term \( e^{2x} \) appears as part of the function. Applying the chain rule, the derivative of \( e^{2x} \) involves the derivative of the inner function \( 2x \).
  • The derivative of \( e^{2x} \) is \( 2e^{2x} \), reflecting how the chain rule guides this calculation.
The chain rule thus greatly facilitates differentiating complex, nested functions, enabling simpler calculations and solutions.
Critical Points
Critical points are where the derivative of a function is zero or undefined. These points hold essential information about the behavior of the function on its graph.
For smooth curves, when the derivative \( f'(x) = 0 \), it indicates a flat tangent line, denoting potential maxima, minima, or saddle points.
Detecting these can help understand where a function increases, decreases, or changes direction.In this specific exercise, setting \( f'(x) = 0 \) solved for \( x = -\frac{1}{2} \).
  • This identifies a critical point on the graph where the tangent is horizontal.
  • It suggests a potential peak or trough — a point of interest in analyzing realistic phenomena or optimizations in functions.
Exploring critical points can reveal local and global behavior of functions, and appreciating this can aid in practical applications like optimization problems.

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Use the properties of logarithms to simplify the following functions before computing \(f^{\prime}(x)\). $$f(x)=\log _{2} \frac{8}{\sqrt{x+1}}$$

Prove the following identities and give the values of \(x\) for which they are true. $$\sin \left(2 \sin ^{-1} x\right)=2 x \sqrt{1-x^{2}}$$

Logistic growth Scientists often use the logistic growth function \(P(t)=\frac{P_{0} K}{P_{0}+\left(K-P_{0}\right) e^{-r_{d}}}\) to model population growth, where \(P_{0}\) is the initial population at time \(t=0, K\) is the carrying capacity, and \(r_{0}\) is the base growth rate. The carrying capacity is a theoretical upper bound on the total population that the surrounding environment can support. The figure shows the sigmoid (S-shaped) curve associated with a typical logistic model. World population (part 1 ) The population of the world reached 6 billion in \(1999(t=0)\). Assume Earth's carrying capacity is 15 billion and the base growth rate is \(r_{0}=0.025\) per year. a. Write a logistic growth function for the world's population (in billions) and graph your equation on the interval \(0 \leq t \leq 200\) using a graphing utility. b. What will the population be in the year 2020? When will it reach 12 billion?

Let \(C(x)\) represent the cost of producing \(x\) items and \(p(x)\) be the sale price per item if \(x\) items are sold. The profit \(P(x)\) of selling x items is \(P(x)=x p(x)-C(x)\) (revenue minus costs). The average profit per item when \(x\) items are sold is \(P(x) / x\) and the marginal profit is dP/dx. The marginal profit approximates the profit obtained by selling one more item given that \(x\) items have already been sold. Consider the following cost functions \(C\) and price functions \(p\). a. Find the profit function \(P\). b. Find the average profit function and marginal profit function. c. Find the average profit and marginal profit if \(x=a\) units are sold. d. Interpret the meaning of the values obtained in part \((c)\). $$\begin{aligned} &C(x)=-0.04 x^{2}+100 x+800, p(x)=200-0.1 x,\\\ &\bar{a}=1000 \end{aligned}$$

A lighthouse stands 500 m off a straight shore and the focused beam of its light revolves four times each minute. As shown in the figure, \(P\) is the point on shore closest to the lighthouse and \(Q\) is a point on the shore 200 m from \(P\). What is the speed of the beam along the shore when it strikes the point \(Q ?\) Describe how the speed of the beam along the shore varies with the distance between \(P\) and \(Q\). Neglect the height of the lighthouse.

See all solutions

Recommended explanations on Math Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.