Chapter 5: Problem 28
Find each indefinite integral. $$ \int x^{2}(8 x+3) d x $$
Short Answer
Expert verified
\( \int x^2(8x + 3) \, dx = 2x^4 + x^3 + C \)
Step by step solution
01
Expand the Integrand
The first step is to simplify the integrand by expanding the expression inside the integral. We start with \( x^2(8x + 3) \), which can be expanded as:\[x^2(8x + 3) = x^2 \cdot 8x + x^2 \cdot 3 = 8x^3 + 3x^2\]Now, the integrand becomes \( 8x^3 + 3x^2 \).
02
Integrate Term by Term
The indefinite integral of a sum of functions is the sum of the integrals of each function. So, integrate each term separately:\[ \int (8x^3 + 3x^2) \, dx = \int 8x^3 \, dx + \int 3x^2 \, dx \]Now, find the integral of each term.
03
Apply the Power Rule for Integration
Use the power rule for integration, which states that \( \int x^n \, dx = \frac{x^{n+1}}{n+1} + C \), where \( C \) is the constant of integration:- For \( \int 8x^3 \, dx \): \[ \int 8x^3 \, dx = 8 \cdot \frac{x^{4}}{4} = 2x^4 \]- For \( \int 3x^2 \, dx \): \[ \int 3x^2 \, dx = 3 \cdot \frac{x^{3}}{3} = x^3 \]
04
Combine the Results with a Constant of Integration
Sum the results obtained from the previous step and include the constant of integration, \( C \):\[\int x^2(8x + 3) \, dx = 2x^4 + x^3 + C\]This is the indefinite integral of the given function.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Power Rule for Integration
The power rule for integration is a fundamental technique in calculus. It's used to find the indefinite integral of functions that are powers of a variable.
This rule states: if you want to integrate a function of the form \( x^n \), you use the formula:
This rule states: if you want to integrate a function of the form \( x^n \), you use the formula:
- \( \int x^n \, dx = \frac{x^{n+1}}{n+1} + C \)
- Increase the exponent \( n \) by 1 to become \( n+1 \).
- Divide the result by the new exponent \( n+1 \).
- Add a constant, \( C \), that accounts for any constant values that could've been differentiated away.
Expanding Expressions
Expanding expressions is a crucial step in solving integrals, especially when dealing with polynomials.
For an expression like \( x^2(8x + 3) \), the first task is to distribute terms:
Keeping expressions expanded minimizes mistakes and provides a clearer path forward.
For an expression like \( x^2(8x + 3) \), the first task is to distribute terms:
- Multiply \( x^2 \) by \( 8x \), resulting in \( 8x^3 \).
- Multiply \( x^2 \) by 3, giving \( 3x^2 \).
Keeping expressions expanded minimizes mistakes and provides a clearer path forward.
Integration Techniques
Integration involves various methods to find the integral of a function, and in this context, it mainly involves simplifying our work through manageable steps.
Here's how the process often unfolds:
Here's how the process often unfolds:
- **Understand the Structure**: Before applying any mathematical operations, it's important to understand the problem’s layout and what each part represents.
- **Simplify the Problem**: As with expanding the expression from \( x^2(8x + 3) \) to \( 8x^3 + 3x^2 \), simplifying makes it easier to apply basic rules.
- **Integrate Step-by-Step**: Break the problem into parts and tackle each separately. Use known techniques like the power rule for straightforward integration.