Why is e^x selected as u and not e^2x (to get du /2 = e^x dx in the problem attached?

Calculus: Early Transcendentals
8th Edition
ISBN:9781285741550
Author:James Stewart
Publisher:James Stewart
Chapter1: Functions And Models
Section: Chapter Questions
Problem 1RCC: (a) What is a function? What are its domain and range? (b) What is the graph of a function? (c) How...
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Why is e^x selected as u and not e^2x (to get du /2 = e^x dx in the problem attached? 

**Given Information:**

The integral function is 

\[
\int \frac{e^{2x}}{e^{2x} + 3e^x + 2} \, dx.
\]

**Calculation:**

Show the integral function as follows:

\[
\int \frac{e^{2x}}{e^{2x} + 3e^x + 2} \, dx \quad \text{(1)}
\]

Consider \( u = e^x \) \quad \text{(2)}

Modify Equation (2):

\[
\ln u = x \quad \text{(3)}
\]

Differentiate both sides of Equation (3):

\[
\frac{1}{u} \, du = dx
\]

Substitute \( u \) for \( e^x \) and \( \frac{1}{u} \, du \) for \( dx \) in Equation (1).
Transcribed Image Text:**Given Information:** The integral function is \[ \int \frac{e^{2x}}{e^{2x} + 3e^x + 2} \, dx. \] **Calculation:** Show the integral function as follows: \[ \int \frac{e^{2x}}{e^{2x} + 3e^x + 2} \, dx \quad \text{(1)} \] Consider \( u = e^x \) \quad \text{(2)} Modify Equation (2): \[ \ln u = x \quad \text{(3)} \] Differentiate both sides of Equation (3): \[ \frac{1}{u} \, du = dx \] Substitute \( u \) for \( e^x \) and \( \frac{1}{u} \, du \) for \( dx \) in Equation (1).
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