Chapter 6: Problem 30
Use integration by parts to find each integral. $$ \int(x+b) e^{a x} d x \quad(a \neq 0) $$
Short Answer
Expert verified
\( \frac{1}{a}(x+b) e^{ax} - \frac{1}{a^2} e^{ax} + C \)
Step by step solution
01
Choose Functions for Integration by Parts
We start by identifying the two parts of the integral: let \( u = x + b \) and \( dv = e^{ax} \, dx \). This choice allows us to simplify the integral when applying the formula for integration by parts.
02
Differentiate and Integrate Functions
Differentiate \( u \) to find \( du \) and integrate \( dv \) to find \( v \):\[ du = dx \] \[ v = \frac{1}{a} e^{ax} \]
03
Apply the Integration by Parts Formula
The integration by parts formula is \( \int u \, dv = uv - \int v \, du \). Substitute the values we have:\[ \int (x+b) e^{ax} \, dx = \left( x+b \right) \left( \frac{1}{a} e^{ax} \right) - \int \left( \frac{1}{a} e^{ax} \right) \, dx \]
04
Calculate the Remaining Integral
The remaining integral is \( \int \frac{1}{a} e^{ax} \, dx \), which simplifies to:\[ \frac{1}{a^2} e^{ax} + C \] (Where \( C \) is the constant of integration).
05
Write the Final Expression
Combine the results to provide the solution:\[ \int (x+b) e^{ax} \, dx = \frac{1}{a}(x+b) e^{ax} - \frac{1}{a^2} e^{ax} + C \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Definite Integral
Definite integrals are a core concept in calculus used to calculate the exact area under a curve between two points. Unlike indefinite integrals, which give a family of functions plus a constant, definite integrals compute a specific numerical value. This value represents the total accumulation, like area or mass, over an interval. To evaluate a definite integral such as \( \int_a^b f(x) \, dx \):
- Begin by finding the indefinite integral, which is the antiderivative of \( f(x) \).
- Use the fundamental theorem of calculus, which states that if \( F(x) \) is the antiderivative of \( f(x) \), then \( \int_a^b f(x) \, dx = F(b) - F(a) \).
- This gives the net area, accounting for sections above and below the x-axis.
Exponential Functions
Exponential functions, characterized by the form \( f(x) = e^{ax} \), are powerful mathematical expressions where the variable is the exponent. The base \( e \) is an irrational constant approximately equal to 2.71828, known for its unique properties in calculus. Key properties of exponential functions include:
- Rapid growth or decay, depending on the sign of the exponent \( a \).
- The derivative of \( e^{ax} \) is straightforward: \( \frac{d}{dx} e^{ax} = a e^{ax} \).
- The integral is similarly direct: \( \int e^{ax} \, dx = \frac{1}{a} e^{ax} + C \).
- Used in various fields, from population modeling in biology to calculating compound interest in finance.
Differentiation
Differentiation is a fundamental process in calculus used to find the rate at which a function changes at any point, also known as the derivative. This process allows us to understand how functions behave and is essential in optimization problems and motion analysis. To differentiate a function, follow these steps:
- Apply the power rule for polynomial terms: \( \frac{d}{dx} x^n = n x^{n-1} \).
- Utilize the product rule when differentiating the product of two functions: if \( u(x) \) and \( v(x) \) are functions, then \( \frac{d}{dx}[u(x)v(x)] = u'(x)v(x) + u(x)v'(x) \).
- Use the chain rule for composite functions: if a function \( y = g(f(x)) \), then \( \frac{dy}{dx} = g'(f(x)) f'(x) \).