Chapter 5: Problem 6
Exer. \(1-8\) : Evaluate the integral using the given substitution, and express the answer in terms of \(x\). $$ \int \frac{1}{(5 x-4)^{10}} d x ; \quad u=5 x-4 $$
Short Answer
Expert verified
The integral is \( -\frac{1}{9(5x - 4)^9} + C \).
Step by step solution
01
Identify the Substitution
We are given the substitution \( u = 5x - 4 \). This substitution simplifies the expression inside the integral.
02
Find du/dx and dx
Differentiate \( u = 5x - 4 \) with respect to \( x \) to find \( \frac{du}{dx} \). Thus, \( \frac{du}{dx} = 5 \), which implies \( dx = \frac{du}{5} \).
03
Substitute Into the Integral
With \( u = 5x - 4 \) and \( dx = \frac{du}{5} \), replace \( (5x - 4) \) with \( u \) and \( dx \) with \( \frac{du}{5} \): \[ \int \frac{1}{u^{10}} \frac{du}{5} = \frac{1}{5} \int u^{-10} \ du \]
04
Integrate with Respect to u
Integrate \( u^{-10} \) term-by-term:\[ \int u^{-10} \ du = \frac{u^{-9}}{-9} + C = -\frac{1}{9u^9} + C \]
05
Substitute Back in Terms of x
Replace \( u \) back with \( 5x - 4 \) to express the integral in terms of \( x \):\[ -\frac{1}{9(5x - 4)^9} + C \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Substitution Method
The substitution method is a powerful tool in integral calculus used to simplify the process of finding integrals. The idea is to transform a complicated integral into a simpler one that is easier to solve. This method involves substituting a part of the integral with a new variable, often making the integration process more straightforward.
Here's how it works:
Here's how it works:
- Identify a part of the integral that can be replaced with a single variable. In our case, we have chosen to set \( u = 5x - 4 \).
- Differentiate the substitution equation to express \( dx \) in terms of \( du \). For instance, if \( u = 5x - 4 \), then \( \frac{du}{dx} = 5 \) implies \( dx = \frac{du}{5} \).
- Replace all occurrences of \( x \) in the original integral with \( u \) and \( dx \) with \( \frac{du}{5} \), which simplifies the problem significantly.
Definite Integral
A definite integral calculates the area under a curve within specified bounds. Unlike indefinite integrals, which represent a family of functions, definite integrals result in a single number.
When evaluating definite integrals using the substitution method, it’s crucial to update the limits of integration to reflect changes in the variable. Here's a quick rundown:
When evaluating definite integrals using the substitution method, it’s crucial to update the limits of integration to reflect changes in the variable. Here's a quick rundown:
- Apply the substitution to transform both the integrand and the limits of integration.
- After integration, if you substituted a variable, make sure to change your answer back to the original variable. This ensures that the final result truly reflects the original problem setup.
- The final result of a definite integral can also be interpreted as the net area bounded by the curve within the limits.
Indefinite Integral
Indefinite integrals represent the most general form of antiderivatives. They denote a family of functions plus a constant of integration \( C \). This constant arises because integrating a function reverses the differentiation process, and differentiation of a constant is zero.
Key points to understand about indefinite integrals:
Key points to understand about indefinite integrals:
- An indefinite integral is essentially asking, "What function, when differentiated, results in the original function inside the integral?"
- The constant of integration \( C \) captures any constant term that would disappear through differentiation.
- In our solved example, integrating \( u^{-10} \) results in an expression that includes this constant \( C \), indicating there are many possible functions that could fit this integral.
Derivative Differentiation
Differentiation is the mathematical process of finding a derivative, which measures how a function changes as its input changes. It's a fundamental concept in calculus, providing insight into rates of change and slopes of curves.
Differentiation is closely linked to integration, as they are essentially inverse operations:
Differentiation is closely linked to integration, as they are essentially inverse operations:
- In the substitution method, we use differentiation to transform expressions — for example, finding \( \frac{du}{dx} \) helps in substituting the variable for integration.
- Understanding how to differentiate correctly is crucial for accurate integration, as it sets up the problem correctly from the start.
- In our exercise, differentiating \( u = 5x - 4 \) to find \( dx \) as \( \frac{du}{5} \) was a pivotal step that allowed us to rewrite the integral in a simpler form.