Chapter 11: Problem 37
Let \(y=f(x)\) be a solution to the differential equation. Determine whether \(y=2 f(x)\) is a solution. $$d y / d x=x$$
Short Answer
Expert verified
No, \( y = 2f(x) \) is not a solution to the differential equation.
Step by step solution
01
Understand the Original Differential Equation
The given differential equation is \( \frac{dy}{dx} = x \). This means that the derivative of the function \( y \) with respect to \( x \) should equal \( x \).
02
Test the Function \( y = f(x) \)
Assume that \( y = f(x) \) satisfies the equation \( \frac{dy}{dx} = x \). Hence, the derivative \( \frac{d}{dx}[f(x)] = x \).
03
Analyze the Function \( y = 2f(x) \)
We need to determine if \( y = 2f(x) \) is also a solution to the differential equation \( \frac{dy}{dx} = x \).
04
Differentiate \( y = 2f(x) \)
Differentiate \( y = 2f(x) \) with respect to \( x \): \( \frac{d}{dx}[2f(x)] = 2 \cdot \frac{d}{dx}[f(x)] = 2x \).
05
Compare with the Initial Differential Equation
The derivative we found is \( 2x \), but the given differential equation states that \( \frac{dy}{dx} = x \). Since \( 2x eq x \), \( y = 2f(x) \) does not satisfy the differential equation.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Solutions to Differential Equations
When tackling differential equations, the goal is to find a function or set of functions known as solutions, that satisfy the equation. In the problem provided, we are given a differential equation, specifically \( \frac{dy}{dx} = x \). This simply means that the rate of change of \(y\) with respect to \(x\) is equal to \(x\). To verify if a function is a solution to this differential equation, we need to check if its derivative matches the right side of the equation.
- Finding Solutions: Solving a differential equation involves determining the function \(y\) that makes the equation true. The function \(f(x)\) was given as a solution because its derivative \( \frac{d}{dx}[f(x)] \) is equal to \(x\), satisfying the equation.
- Testing Other Functions: The exercise involved checking if \(y = 2f(x)\) meets the criteria. By differentiating, we found \( \frac{d}{dx}[2f(x)] = 2x \), which does not match the original equation's form \( \frac{dy}{dx} = x \). Hence, \(y = 2f(x)\) is not a solution.
Derivatives
Derivatives are a fundamental concept in calculus used to measure how a function changes as its input changes. They are especially crucial in differential equations, where they directly relate to the solution of the equation.
- Understanding Derivatives: The derivative \( \frac{dy}{dx} \) of a function \(y = f(x)\) describes the rate at which \(y\) changes with respect to \(x\). It's like a slope, telling us how steep the curve of the function is at a given point.
- Application in Differential Equations: In the context of our exercise, finding the derivative of \(y = f(x)\) helps us verify whether the function satisfies the differential equation \( \frac{dy}{dx} = x \).
- Checking Work: When we computed \( \frac{d}{dx}[2f(x)] = 2x \), we compared this with the original equation. Since \(2x eq x\), this confirmed that \(y = 2f(x)\) is not a solution.
Mathematical Functions
Mathematical functions are expressions that relate inputs to outputs, often used to describe real-world relationships and phenomena. Understanding these functions is key to solving differential equations.
- Functions as Solutions: A function like \(f(x)\) can be a solution to a differential equation if its derivative satisfies the equation. The function \(f(x)\) in our example did just that.
- Modifying Functions: When we considered \(y = 2f(x)\), we essentially modified the function to test its validity as a solution. This highlights how slight changes in functions can affect whether they satisfy certain equations.
- Generalization and Use: Functions provide a general solution to many equations and understanding their behavior, through derivatives and integrals, is essential in math, physics, engineering, and more.