Chapter 6: Problem 10
For Activities 5 through \(16,\) evaluate the improper integral. $$ \int_{-x}^{-10} 4 x^{-3} d x $$
Short Answer
Expert verified
The value of the improper integral is \(-\frac{2}{x^2} + 0.02\).
Step by step solution
01
Understand the Problem
The given problem asks for the evaluation of an improper integral of the function \(4x^{-3}\) from \(-x\) to \(-10\). This integral is improper because the upper limit of the integral, \(-x\), could be a point where the integrand becomes undefined or has infinity.
02
Setup the Integral
The integral is given by:\[\int_{-x}^{-10} 4x^{-3} \, dx\] Here, \(-10\) is the lower limit, and \(-x\) is the upper limit.
03
Find the Antiderivative
To integrate \(4x^{-3}\), we find the antiderivative. The antiderivative of \(x^{-3}\) is \(-\frac{1}{2}x^{-2}\). Thus, the antiderivative of \(4x^{-3}\) is:\[-2x^{-2}\]
04
Evaluate the Definite Integral
Substitute the limits into the antiderivative:\[\left[ -2x^{-2} \right]_{-10}^{-x} = -2(-x)^{-2} - \left( -2(-10)^{-2} \right)\]Calculate each term:\[= -2(-x)^{-2} + 2(0.01) \]\[= -\frac{2}{x^2} + 0.02\]
05
Simplify the Result
The expression for the definite integral becomes:\[-\frac{2}{x^2} + 0.02\]
06
Interpret the Result
With the expression \(-\frac{2}{x^2} + 0.02\), note that the value depends on \(x\). Since this is an improper integral problem, make sure the integral evaluates to a finite number when x approaches values that don't cause division by zero.
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.
Antiderivative
An antiderivative of a function is like its 'reverse' derivative. If you take a derivative to find how a function is changing, finding an antiderivative tells you about the original function from which it came. The process is often known as integration.When you have a function such as \(4x^{-3}\), finding its antiderivative means looking for a function whose derivative is \(4x^{-3}\). For this problem, the antiderivative of \(x^{-3}\) is \(-\frac{1}{2}x^{-2}\). Therefore, the antiderivative of \(4x^{-3}\) becomes \(-2x^{-2}\).
- Key Idea: Differentiation and antiderivatives are opposites.
- Process: Determine the function that gives you the original upon differentiation.
Definite Integral
A definite integral is an integral with upper and lower limits, and it represents the accumulation of quantities, like area under a curve, between these limits. For the given exercise, the definite integral is written as:\[\int_{-x}^{-10} 4x^{-3} \, dx\]With definite integrals, you often substitute the limits into the antiderivative. For instance, substituting the limits into \(-2x^{-2}\), we get:\[\left[ -2x^{-2} \right]_{-10}^{-x} = -2(-x)^{-2} - \left( -2(-10)^{-2} \right)\]
- Importance: Definite integrals provide a specific numerical value.
- Calculation: Substitute and simplify using the antiderivative and the limits.
Upper Limit
The upper limit in a definite integral indicates where the integration stops along the x-axis. In this exercise, the upper limit is \(-x\). It's imperative to recognize how changes to the upper limit affect the evaluation of the integral.For the improper integral in the exercise, the function might become undefined if \(x\) ultimately causes a division by zero. This is what differentiates improper integrals from proper ones.
- Role of Upper Limit: Defines the endpoint of integration. Changes in this limit alter the value of the integral.
- Improper Integral Impact: If the upper limit causes the integrand to be undefined (e.g., division by zero), the integral might not converge to a finite value.