Chapter 7: Problem 9
Evaluate the indefinite integral by making the given substitution. $$ \int e^{2 x+3} d x, \text { with } u=2 x+3 $$
Short Answer
Expert verified
The indefinite integral is \( \frac{1}{2} e^{2x+3} + C \).
Step by step solution
01
Identify the Substitution
In this problem, the substitution given is \( u = 2x + 3 \). This means we need to replace \( 2x + 3 \) with \( u \) in the integral.
02
Differentiate the Substitution
Differentiate \( u = 2x + 3 \) with respect to \( x \) to find \( du \). The derivative is \( \frac{du}{dx} = 2 \).
03
Solve for dx
Rearrange the derivative for \( dx \) as follows:\[ dx = \frac{du}{2} \]
04
Substitute in the Integral
Substitute \( u \) and \( dx \) into the integral. It turns from\[ \int e^{2x+3} \, dx \] to \[ \int e^{u} \, \frac{du}{2} \] or \[ \frac{1}{2} \int e^{u} \, du \] .
05
Integrate with respect to u
Integrate \( \frac{1}{2} \int e^u \, du \). The result is \[ \frac{1}{2} e^u + C \] where \( C \) is the constant of integration.
06
Back-Substitute for u
Replace \( u \) with the original expression \( 2x + 3 \). The solution becomes\[ \frac{1}{2} e^{2x+3} + C \].
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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 technique used to simplify the process of integration. It works by replacing a complex expression with a simpler variable, making the integral easier to solve. In the given exercise, the substitution is given as \( u = 2x + 3 \).
- This method often involves identifying a part of the integrand (the function inside the integral) that can be replaced by a single variable, \( u \).
- Once the substitution is chosen, you differentiate it to find \( du \). This step is essential as it helps in changing the integration variable from \( x \) to \( u \).
- In our exercise, differentiating \( u = 2x + 3 \) gives \( \frac{du}{dx} = 2 \), leading to \( dx = \frac{du}{2} \).
Integration
Integration is the mathematical process of finding the integral of a function. In the case of indefinite integration, the result includes a constant, \( C \), representing an infinite set of possible solutions.
- With the substitution step complete, our integral \( \int e^{2x+3} \, dx \) changes to \( \frac{1}{2} \int e^u \, du \).
- The integrand \( e^u \) is a basic exponential function, which simplifies the integration.
Exponential Function
Exponential functions are a key part of calculus and often appear in integration problems. These functions take the form \( e^x \), where \( e \) is the base of natural logarithms.
- They have unique properties, such as the derivative and integral of \( e^x \) both being \( e^x \), which greatly simplifies the process of calculus operations.
- In our problem, after substituting and integrating, \( e^u \) becomes the focus, and its integral is \( e^u \).