Chapter 28: Problem 23
In Exercises \(3-26,\) integrate each of the given functions. $$\int(x+4)^{8}(x+5) d x$$
Short Answer
Expert verified
The integral is \( \frac{(x+4)^{10}}{10} + \frac{(x+4)^9}{9} + C \).
Step by step solution
01
Identify Parts for Substitution
Recognize that the integrand is the product of two functions, \( (x+4)^8 \text{ and } (x+5)\). We can use substitution to simplify this. Let's set \( u = x+4 \) and thus \( du = dx\). Observe that \((x+5) = (u+1)\).
02
Substitute and Adjust Limits
After substitution, the integral becomes \( \int u^8 (u+1) \, du \). This step simplifies the product of the functions before integration.
03
Expand the Integrand
Expand the integrand \( u^8(u+1) = u^9 + u^8 \). This makes the integral separable, allowing us to integrate term by term.
04
Integrate Term by Term
Integrate each term separately: \( \int u^9 \, du = \frac{u^{10}}{10} \)and\( \int u^8 \, du = \frac{u^9}{9} \).
05
Combine the Integrals
Combine the separate integrals to form: \( \frac{u^{10}}{10} + \frac{u^9}{9} \).
06
Substitute Back to Original Variable
Revert the substitution \( u = x+4 \) back into the function: \( \frac{(x+4)^{10}}{10} + \frac{(x+4)^9}{9} + C \), where \( C \) is the arbitrary constant.
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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 used in integration to simplify complex integrals by changing variables. It often makes an integral easier to solve by reducing it to a more recognisable form. In the given problem, we are dealing with the integrand
- \((x+4)^8 (x+5)\)
- \(u = x+4\)
- \((x+5)\) into \((u+1)\).
- \(\int u^8(u+1) du\).
Polynomial Integration
Polynomial integration involves integrating functions of the form
- \(ax^n\)
- \(a\) is a constant and \(n\) is an integer.
- \(\int ax^n dx = \frac{ax^{n+1}}{n+1} + C\),
- \(C\) is the constant of integration.
- \(u^8(u+1)\) to \(u^9 + u^8\).
- \(\int u^9 \, du\) results in \(\frac{u^{10}}{10}\)
- \(\int u^8 \, du\) results in \(\frac{u^9}{9}\).
- \(u\).
Definite and Indefinite Integrals
Integrals are classified into two main types: definite and indefinite. In indefinite integrals, as seen in our exercise, the integral does not have bounds. This generally results in a family of functions plus a constant
- \(C\).
- Thus, \(\int u^9 du\) results in \(\frac{u^{10}}{10} + C\).
- \(C\), which represents an unknown constant that could arise from any constant term added during differentiation.
Step-by-Step Solutions
Step-by-step solutions are incredibly valuable, particularly as they break down complex problems into smaller, more manageable parts. This method acts as a roadmap, guiding you through the integration process clearly and sequentially. In our exercise, we:
- Identified the parts for substitution, setting \(u = x+4\), and noticed \((x+5) = (u+1)\).
- Substituted these into the integral, simplifying our problem.
- Expanded the integrand, allowing polynomial integration of each term separately.
- Integrated each term one by one, using the rules of polynomial integration.
- Finally combined the results and reverted the substitution, converting back to the original variable \(x\).