Chapter 5: Problem 89
Suppose that \(\int_{0}^{4} f(x) d x=5\) and \(\int_{0}^{2} f(x) d x=-3,\) and \(\int_{0}^{4} g(x) d x=-1\) and \(\int_{0}^{2} g(x) d x=2 .\) In the following exercises, compute the integrals. \(\int_{2}^{4}(f(x)+g(x)) d x\)
Short Answer
Expert verified
The integral \(\int_{2}^{4}(f(x)+g(x)) \, dx\) is 5.
Step by step solution
01
Use the Integral Addition Property
We start by acknowledging the property of integration that allows us to separate the integral of a sum: \(\int (f(x) + g(x)) \, dx = \int f(x) \, dx + \int g(x) \, dx\). This means that we can break down the problem into two parts: \(\int_{2}^{4} f(x) \, dx\) and \(\int_{2}^{4} g(x) \, dx\).
02
Apply the Property of Definite Integrals
Using the property of definite integrals, we can express \(\int_{2}^{4} f(x) \, dx\) as \(\int_{0}^{4} f(x) \, dx - \int_{0}^{2} f(x) \, dx\). Similarly, express \(\int_{2}^{4} g(x) \, dx\) as \(\int_{0}^{4} g(x) \, dx - \int_{0}^{2} g(x) \, dx\).
03
Calculate \(\int_{2}^{4} f(x) \, dx\)
Substitute the given values: \(\int_{2}^{4} f(x) \, dx = \int_{0}^{4} f(x) \, dx - \int_{0}^{2} f(x) \, dx = 5 - (-3) = 5 + 3 = 8\).
04
Calculate \(\int_{2}^{4} g(x) \, dx\)
Substitute the given values: \(\int_{2}^{4} g(x) \, dx = \int_{0}^{4} g(x) \, dx - \int_{0}^{2} g(x) \, dx = -1 - 2 = -3\).
05
Sum the Results
Now add the two results from Steps 3 and 4:\(\int_{2}^{4}(f(x) + g(x)) \, dx = \int_{2}^{4} f(x) \, dx + \int_{2}^{4} g(x) \, dx = 8 + (-3) = 5\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Integral Addition Property
The Integral Addition Property is a fundamental concept in calculus. It allows you to split the integral of a sum of functions into the sum of individual integrals. This is especially handy when dealing with complex expressions. Let's break it down!
- When you have an integral such as \(\int (f(x) + g(x)) \, dx\), you can rewrite it as \(\int f(x) \, dx + \int g(x) \, dx\).
- This property works for both definite and indefinite integrals, simplifying calculations.
- It's especially useful when you have bounds on the integral like \(\int_{2}^{4}(f(x) + g(x)) \, dx\).
Properties of Definite Integrals
Definite integrals have specific properties that can be harnessed to simplify complex integral calculations. Let's explore key aspects that were pivotal in solving the given exercise.
- One notable property is the ability to compute the definite integral over a specific interval by subtracting two integrals. It follows the formula: \(\int_{a}^{b} f(x) \, dx = \int_{c}^{b} f(x) \, dx - \int_{c}^{a} f(x) \, dx\).
- This means you can find \(\int_{2}^{4} f(x) \, dx\) by using known integrals like \(\int_{0}^{4} f(x) \, dx\) and \(\int_{0}^{2} f(x) \, dx\).
- The ability to manipulate the limits of integration using basic arithmetic is crucial for breaking down problems.
Step-by-Step Calculation
Approaching each integral problem methodically through a step-by-step calculation strategy is efficient and ensures accuracy. Here’s how the exercise is solved stepwise:
This step-by-step approach clarifies how to use integral properties efficiently, ensuring each calculation builds logically on the last, leading neatly to the final result.
Step 1: Apply the Integral Addition Property
The problem is broken into two separate integrals by applying the addition property: \(\int_{2}^{4} f(x) \, dx\) and \(\int_{2}^{4} g(x) \, dx\).Step 2: Use Properties of Definite Integrals
Calculate each integral over \(2\) to \(4\) by subtracting known values: \(\int_{2}^{4} f(x) \, dx\) using \(\int_{0}^{4} f(x) \, dx\) and \(\int_{0}^{2} f(x) \, dx\); similarly for \(g(x)\). The calculations are:- For \(f(x)\): \(\int_{2}^{4} f(x) \, dx = 5 - (-3) = 8\)
- For \(g(x)\): \(\int_{2}^{4} g(x) \, dx = -1 - 2 = -3\)
Step 3: Sum the Results
Finally, add the integrals from steps 3 and 4 to find \(\int_{2}^{4}(f(x) + g(x)) \, dx = 8 + (-3) = 5\).This step-by-step approach clarifies how to use integral properties efficiently, ensuring each calculation builds logically on the last, leading neatly to the final result.