# Improper Integral of 3*e^(-3x) from 0 to Infinity | Summary and Q&A

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March 31, 2021
by
The Math Sorcerer
Improper Integral of 3*e^(-3x) from 0 to Infinity

## TL;DR

The video discusses how to determine if an improper integral converges or diverges and find its value.

## Key Insights

• ♾️ Improper integrals can be evaluated by replacing the infinity symbol with a variable and calculating the limit as that variable approaches infinity.
• ☺️ The integration rule for e to the ax states that the integral can be found by dividing the expression by a.
• ❓ In the given example, the improper integral converges to a value of 1.
• ♾️ If the limit of the integral evaluates to infinity, negative infinity, or does not exist, the integral is said to diverge.
• #️⃣ The exponential function e to the power of a number times x plays a key role in evaluating improper integrals.
• ⛔ Understanding how limits approach finite numbers or infinity is essential in determining the convergence of integrals.
• 📏 By manipulating exponentials and applying integration rules, improper integrals can be simplified and evaluated.

## Transcript

in this problem we have an improper integral and the question is does it converge or does it diverge and if it converges you know what is its value so we'll start by trying to evaluate it so recall that whenever you have an integral like this which is improper because of the infinity what you can do is you can replace the infinity symbol with a var... Read More

### Q: How can an improper integral be evaluated by replacing the infinity symbol with a variable?

To evaluate an improper integral, you can replace the infinity symbol with a variable (such as b) and then calculate the limit as that variable approaches infinity.

### Q: What is the integration rule for e to the power of a number times x?

The integration rule states that for e to the ax dx (where a is not equal to 0), the integral can be found by dividing the expression by a. So, 3 e to the negative 3x dx becomes 3 e to the negative 3x divided by negative 3.

### Q: How does the limit of the function approach 1?

By substituting the value of b into the expression and subtracting the value of e to the negative 3 times 0, the limit as b approaches infinity simplifies to negative e to the negative 3b + 1. As b approaches infinity, this expression approaches 0 + 1, which is equal to 1.

### Q: What conclusion can be drawn about the convergence of the integral?

Since the limit of the integral evaluates to a finite number (1), it can be concluded that the integral converges.

## Summary & Key Takeaways

• The video explains how to replace the infinity symbol in an improper integral with a variable and evaluate the limit as that variable approaches infinity.

• By using the integration rule for e to the power of a number times x, the integral can be simplified.

• After performing the necessary calculations, it is determined that the integral converges to a value of 1.