Chapter 28: Problem 17
Integrate each of the given functions. $$\int_{1}^{3} 3 e^{2 x}\left(e^{-2 x}-1\right) d x$$
Short Answer
Expert verified
The result of the integral is: \(6 - \frac{3}{2}(e^6 - e^2)\).
Step by step solution
01
Distribute the Multiplier
Let's first distribute the constant 3 inside the integral by applying it to both terms within the parentheses. \[\int_{1}^{3} 3e^{2x}(e^{-2x} - 1) dx = \int_{1}^{3} 3e^{2x} \cdot e^{-2x} dx - \int_{1}^{3} 3e^{2x} dx\]
02
Simplify Exponents
Each term in the integral can be further simplified. The first term involves the product of exponentials:\[3e^{2x} \cdot e^{-2x} = 3e^{0} = 3\]So, the first integral becomes a constant function.The entire integral becomes:\[\int_{1}^{3} 3 \, dx - \int_{1}^{3} 3e^{2x} \, dx\]
03
Integrate the Constant Function
Integrate the constant function 3 over the interval from 1 to 3. This simplifies to:\[3 \int_{1}^{3} dx = 3[x]_{1}^{3} = 3(3-1) = 6\]
04
Integrate the Exponential Function
Integrate the function \(3e^{2x}\) from 1 to 3. We need to account for the coefficient from the chain rule:\[\int 3e^{2x} \, dx = \frac{3}{2}e^{2x} + C\]Evaluate this from 1 to 3:\[\frac{3}{2} [e^{2x}]_{1}^{3} = \frac{3}{2}(e^6 - e^2)\]
05
Subtract the Integrals
Now, subtract the result from Step 4 from the result of Step 3:\[6 - \frac{3}{2}(e^6 - e^2)\]Simplify this to find the final answer.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Distributing Constants
Distributing constants is a fundamental step when integrating, especially when dealing with products. In this exercise, we encounter a multiplier outside the parentheses, which needs to be distributed properly inside. Here, we start with the expression \(3e^{2x}(e^{-2x} - 1)\). By distributing the 3 (constant) to each term inside the parentheses, we simplify our integration process.
- Distribute the 3 to \(e^{2x} imes e^{-2x}\)
- Then distribute the 3 to \(-1\)
Simplifying Exponents
Exponential expressions often appear complex but can be simplified using basic rules of exponents. Consider \(3e^{2x} imes e^{-2x}\). According to exponent rules:
- The product of powers with the same base is the base raised to the sum of the exponents. So, \(e^{2x} imes e^{-2x} = e^{0} = 1\).
- Thus, \(3e^{2x} \cdot e^{-2x}\) simplifies to 3.
Integrating Constant Functions
When integrating constant functions, it is relatively straightforward. A constant function, like 3, over an interval such as from 1 to 3, requires simple arithmetic. We use the formula for integrating constants: \[ \int_{a}^{b} c \, dx = c[x]_{a}^{b} \]In this case, \(c = 3\), so integrating from 1 to 3 becomes:
- Calculate \(3[x]_{1}^{3} = 3(3 - 1) = 6\)
- This is the result for the first simplified integral term.
Integrating Exponential Functions
Exponential functions, while complex, become manageable with proper techniques. Here, we integrate \(3e^{2x}\). First, we use the chain rule from calculus:
- When integrating \(3e^{2x}\), note the inner derivative \(d/dx(2x) = 2\).
- We adjust for this by introducing a factor, leading to \(\frac{3}{2}e^{2x}\).
Definite Integrals
Definite integrals provide a numerical value representing the area under a curve, between specific bounds. By combining the results of our calculations, we subtract the exponential integral from the constant's result:
- The first term gave us 6.
- The second term resulted in \(\frac{3}{2}(e^6 - e^2)\).