Chapter 3: Problem 105
Give an example of: Two functions \(f(x)\) and \(g(x)\) such that $$ \frac{d}{d x}(f(x)+g(x))=2 x+3 $$
Short Answer
Expert verified
Example functions are \(f(x) = x^2 + 1\) and \(g(x) = 3x + C - 1\).
Step by step solution
01
Understanding the Derivative
The exercise asks us to find two functions \(f(x)\) and \(g(x)\) such that the derivative of their sum is given by \(\frac{d}{dx}(f(x)+g(x))=2x+3\). This means we need to find functions whose combined derivative with respect to \(x\) is equal to \(2x+3\).
02
Integrating the Given Derivative
To find \(f(x)\) and \(g(x)\), we can first integrate the given expression \(2x+3\) with respect to \(x\). Integrating, we have \(\int (2x+3) \, dx\).
03
Solving the Integration
The integral \(\int (2x+3) \, dx = x^2 + 3x + C\), where \(C\) is the constant of integration. This integral represents the sum \(f(x) + g(x)\), so both functions together form this expression.
04
Choosing Functions
To find individual functions \(f(x)\) and \(g(x)\), we can choose any two functions that combine to form \(x^2 + 3x + C\). For instance, let \(f(x) = x^2 + 1\) and \(g(x) = 3x + C - 1\).
05
Verifying the Solution
Check that the derivative of \(f(x) + g(x)\) is indeed \(2x+3\). Differentiate \(f(x) + g(x)\): \(\frac{d}{dx}(x^2 + 3x + C) = 2x + 3\), which matches the original condition. Thus, our choice of functions is valid.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Antiderivative
The antiderivative is a fundamental concept in calculus. Often referred to as the "indefinite integral," it represents the reverse process of differentiation. When we take the derivative of a function, we find the rate of change. The antiderivative, on the other hand, helps us understand what function could have produced a given derivative.
In this exercise, we are tasked with finding functions whose derivative summates to a specific expression, specifically \(2x+3\). To do so, we compute the antiderivative. This tells us that the original function could be any function whose derivative equals \(2x+3\).
In this exercise, we are tasked with finding functions whose derivative summates to a specific expression, specifically \(2x+3\). To do so, we compute the antiderivative. This tells us that the original function could be any function whose derivative equals \(2x+3\).
- The integral \(\int (2x + 3) \, dx\) is calculated to find an antiderivative.
- The result \(x^2 + 3x + C\) suggests all possible functions that fit this criterion.
Constitution of functions
The constitution of functions refers to the formulation of distinct functions that, when combined, satisfy a given condition. In our particular problem, we're looking to find two functions, \(f(x)\) and \(g(x)\), that together add up to the antiderivative we found earlier, \(x^2 + 3x + C\).
This means we're essentially decomposing the entire expression into two parts, each being a separate function.
This means we're essentially decomposing the entire expression into two parts, each being a separate function.
- We can choose \(f(x) = x^2 + 1\) as one of these parts.
- The remaining part comes naturally, as \(g(x) = 3x + C - 1\), ensuring that both add up to the full expression \(x^2 + 3x + C\).
Derivative
The derivative is a central concept that measures how a function changes as its input changes. In this context, it tells us the rate of change of the combined function \(f(x) + g(x)\) over intervals of \(x\). It allows us to verify whether our constructed functions meet the original problem's requirements.
The derivative of a sum of functions is equal to the sum of their derivatives. Here, differentiating \(f(x) + g(x) = x^2 + 3x + C\) gives us:
The derivative of a sum of functions is equal to the sum of their derivatives. Here, differentiating \(f(x) + g(x) = x^2 + 3x + C\) gives us:
- \(\frac{d}{dx}(x^2 + 3x + C) = 2x + 3\).
- This derivative matches the condition stated in the exercise, confirming our function choice.
Constant of Integration
The constant of integration, represented by \(C\), is a critical component of indefinite integrals. Its presence acknowledges that there are infinitely many potential antiderivatives for a given function, differing only by a constant. It's the "± C" that often appears when finding antiderivatives.
In the exercise, \(C\) allows flexibility in the function \(f(x) + g(x) = x^2 + 3x + C\).
In the exercise, \(C\) allows flexibility in the function \(f(x) + g(x) = x^2 + 3x + C\).
- This means our constructed functions can absorb this constant, such as into \(g(x)\) by stating it as \(3x + C - 1\).
- This flexibility also allows adaptability in constructing functions that still satisfy the conditions.