/*! 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 66 Using properties of ln, find a s... [FREE SOLUTION] | 91Ó°ÊÓ

91Ó°ÊÓ

Using properties of ln, find a substitution \(w\) and constants \(k, n\) so that the integral has the form. $$\int k w^{n} \ln w d w$$ $$\int(2 x+1)^{3} \ln \frac{1}{\sqrt{2 x+1}} d x$$

Short Answer

Expert verified
Substitute \( w = 2x+1 \), with \( k = -\frac{1}{4} \) and \( n = 3 \).

Step by step solution

01

Simplify the Logarithmic Expression

The expression inside the logarithm is \( \ln \frac{1}{\sqrt{2x+1}} \). By using the property \( \ln \frac{1}{a} = -\ln a \) and \( \ln a^c = c\ln a \), we can rewrite this as \( -\frac{1}{2}\ln(2x+1) \).
02

Substitution for Simplification

Let \( w = 2x+1 \), then \( \ln \frac{1}{\sqrt{2x+1}} \) becomes \( -\frac{1}{2}\ln w \). This substitution also simplifies \( (2x+1)^3 \) to \( w^3 \).
03

Differentiate for Substitute \( dx \)

We need to express \( dx \) in terms of \( dw \). Since \( w = 2x+1 \), differentiating both sides gives \( dw = 2dx \), or equivalently, \( dx = \frac{1}{2}dw \).
04

Substitute and Rewrite the Integral

Substitute \( w = 2x+1 \) and \( dx = \frac{1}{2} dw \) into the integral to get: \( \int (w^3)\left(-\frac{1}{2}\ln w\right) \cdot \frac{1}{2}dw \).
05

Identify Constants \( k, n \)

Rewriting the integral gives \( \int -\frac{1}{4} w^3 \ln w \, dw \). The constant \( k = -\frac{1}{4} \) and the power of \( w \) is \( n = 3 \).

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.

logarithmic properties
Logarithmic properties are powerful tools for simplifying many mathematical expressions, especially those involving natural logarithms, like \( \ln \). Understanding these properties can make complex functions much more manageable. Here are some key logarithmic properties used in calculus:
  • \( \ln(\frac{1}{a}) = -\ln(a) \): This states that the logarithm of a reciprocal is the negative of the logarithm.
  • \( \ln(a^c) = c\ln(a) \): Known as the power rule, it says the logarithm of a power can be brought out as a coefficient.
In our exercise, the property \( \ln(\frac{1}{\sqrt{2x+1}}) \) was used to simplify into \( -\frac{1}{2} \ln(2x+1) \), utilizing the law that converts a square root into a fractional exponent and transfers it as a multiplier. These properties are essential in breaking down logarithmic expressions into a form which is easier to integrate.
integration techniques
Integration techniques are methods employed to evaluate integrals, which are fundamental in calculus. One critical skill is to recognize when to use specific techniques, such as substitution, integration by parts, or partial fraction decomposition.For this problem, integration includes identifying and simplifying terms to convert the integral into a standard form. Once simplified through the logarithmic properties, the task becomes more straightforward. Here are some steps involved in integration techniques:
  • Rewrite complex expressions using known mathematics properties.
  • Look for substitutions that simplify the integral into a recognizable form.
  • Manipulate the differential (\( dx \)) and corresponding algebraic terms to match the integral's structure.
The problem applies the method of substitution, going from variables \( x \) to \( w \), which simplifies both the logarithmic term and the cubic polynomial, aligning it with a known integral format.
substitution method
The substitution method is an integration technique akin to reversing the chain rule. It is used to simplify integrals by introducing a new variable. Substitution works well when the integral includes a function and its derivative.In this exercise, we apply substitution by setting \( w = 2x+1 \). Here's why it's beneficial:
  • This transforms the expression \( \ln \frac{1}{\sqrt{2x+1}} \) into a simpler form \( -\frac{1}{2} \ln w \), turning the integral into one involving a single log term.
  • Converting the differential, we find \( dx = \frac{1}{2} dw \). This adjustment is necessary to ensure everything is in terms of \( w \).
  • Simplifies \( (2x+1)^3 \) to \( w^3 \), making the exponentiation straightforward.
The substitution method streamlines innumerable calculus problems by reducing the complexity of integration, making it an essential tool for any calculus student to master.

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

Explain what is wrong with the statement. The table can be used to evaluate \(\int \sin x / x \, d x\)

Find an expression for the integral which contains \(g\) but no integral sign. $$\int g^{\prime}(x)(g(x))^{4} d x$$

Over the past fifty years the carbon dioxide level in the atmosphere has increased. Carbon dioxide is believed to drive temperature, so predictions of future carbon dioxide levels are important. If \(C(t)\) is carbon dioxide level in parts per million (ppm) and \(t\) is time in years since \(1950,\) three possible models are: \(^{1}\) I \(C^{\prime}(t)=1.3\) II \(C^{\prime}(t)=0.5+0.03 t\) III \(C^{\prime}(t)=0.5 e^{0.02 z}\) (a) Given that the carbon dioxide level was 311 ppm in \(1950,\) find \(C(t)\) for each model. (b) Find the carbon dioxide level in 2020 predicted by each model.

The rate at which water is flowing into a tank is \(r(t)\) gallons/minute, with \(t\) in minutes. (a) Write an expression approximating the amount of water entering the tank during the interval from time \(t\) to time \(t+\Delta t,\) where \(\Delta t\) is small. (b) Write a Riemann sum approximating the total amount of water entering the tank between \(t=0\) and \(t=5 .\) Write an exact expression for this amount. (c) By how much has the amount of water in the tank changed between \(t=0\) and \(t=5\) if \(r(t)=20 e^{a+2 t} ?\) (d) If \(r(t)\) is as in part (c), and if the tank contains 3000 gallons initially, find a formula for \(Q(t),\) the amount of water in the tank at time \(t\)

Find a substitution \(w\) and constants \(a, b, k\) so that the integral has the form \(\int_{a}^{b} k f(w) d w\). $$\int_{0}^{\pi} f(\cos x) \sin x d x$$

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.