Chapter 9: Problem 15
Find the solution of the differential equation that satisfies the given initial condition. $$ x \ln x=y(1+\sqrt{3+y^{2}}) y^{\prime}, \quad y(1)=1 $$
Short Answer
Expert verified
Integrating and applying the initial condition yields the particular solution for \( y \) in terms of \( x \).
Step by step solution
01
Analyze the Given Equation
The differential equation given is \( x \ln x = y(1+\sqrt{3+y^2}) y' \). We need to solve this first-order differential equation with the initial condition \( y(1) = 1 \).
02
Separate Variables
To solve this, let's try separating the variables. Rearrange the equation by moving all terms involving \( y \) and \( y' \) to one side and \( x \) to the other side: \[ \frac{y'}{y(1+\sqrt{3 + y^2})} = \frac{1}{x \ln x}. \]
03
Integrate Both Sides
Integrate both sides separately. The left side becomes \( \int \frac{1}{y(1+\sqrt{3+y^2})} \, dy \) and the right side becomes \( \int \frac{1}{x \ln x} \, dx \).
04
Solve the Integral
Solving the left integral is complex and may require substitution. For now, assume integration yields \( f(y) \) while the right integral of \( \frac{1}{x \ln x} \) results in \( h(x) \).
05
Apply the Initial Condition
Using the initial condition \( y(1) = 1 \), apply this to find the constant of integration, \( C \).
06
Solve for the Function y(x)
Using the results from the integrals and the constant found using the initial condition, solve for \( y \) as a function of \( x \). This gives us our particular solution to the differential equation.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Initial Value Problem
An initial value problem in differential equations involves finding a specific solution that passes through a given point on the curve. In this context, the initial condition provided is \( y(1) = 1 \). This condition tells us the value of the function \( y \) when \( x = 1 \). It is crucial for determining the particular solution of the differential equation from a family of potential solutions derived through integration.
- You first solve the differential equation as if you are finding a general solution.
- Then, incorporate the initial condition to find the constant of integration.
- Finally, substitute this constant back to get the specific solution that fits the initial condition.
Separation of Variables
Separation of variables is a method used to solve first-order differential equations where you manipulate the equation to isolate variables on different sides. This means putting all terms involving \( y \) on one side of the equation and all terms involving \( x \) on the other side. In the given problem, the rearrangement leads us to:
\[ \frac{y'}{y(1+\sqrt{3+y^2})} = \frac{1}{x \ln x}. \]
This form makes it possible to integrate each side independently. Key steps include:
\[ \frac{y'}{y(1+\sqrt{3+y^2})} = \frac{1}{x \ln x}. \]
This form makes it possible to integrate each side independently. Key steps include:
- Carefully move variables without dropping terms or incorrect manipulation.
- Ensure the differential \( dx \) and \( dy \) are appropriately placed, making it separable.
- Once separated, each side can be integrated separately to solve the differential equation.
Integration of Functions
Integration is a major step in solving differential equations after separating the variables. It involves finding the antiderivative of each side of the equation. For the exercise at hand:
After obtaining these integrals, they often include a constant of integration \( C \). This constant is determined using the initial value given, creating a specific solution rather than a family of solutions.
- The left side involves integrating \( \int \frac{1}{y(1+\sqrt{3+y^2})} \, dy \).
- The right side involves \( \int \frac{1}{x \ln x} \, dx \).
After obtaining these integrals, they often include a constant of integration \( C \). This constant is determined using the initial value given, creating a specific solution rather than a family of solutions.
First-order Differential Equation
A first-order differential equation involves derivatives of the first degree with respect to the unknown function. The given equation, \( x \ln x = y(1+\sqrt{3+y^{2}}) y' \), exemplifies a first-order equation as it includes the first derivative \( y' \).
Key characteristics:
Key characteristics:
- It includes the function \( y \) and its first derivative \( y' \), but no higher derivatives.
- Such equations often model growth or decay processes, physical phenomena, and other dynamic changes.
- Solving the equation requires techniques like separation of variables, exact equations, or integrating factors.