Math Problem Statement

integrating factor

Solution

Great! Let's solve the given differential equation using the integrating factor method.

The given equation is:

(x+2)y=58y4xy(x + 2) y' = 5 - 8y - 4xy

First, we rewrite it in the standard linear form:

y+P(x)y=Q(x)y' + P(x)y = Q(x)

We need to divide the whole equation by x+2x + 2:

y+4x+8x+2y=5x+2y' + \frac{4x + 8}{x + 2} y = \frac{5}{x + 2}

This simplifies to:

y+4y=5x+2y' + 4y = \frac{5}{x + 2}

Now, this is a linear differential equation of the form y+P(x)y=Q(x)y' + P(x)y = Q(x), where P(x)=4P(x) = 4 and Q(x)=5x+2Q(x) = \frac{5}{x + 2}.

Step 1: Find the integrating factor

The integrating factor μ(x)\mu(x) is given by:

μ(x)=eP(x)dx=e4dx=e4x\mu(x) = e^{\int P(x) dx} = e^{\int 4 \, dx} = e^{4x}

Step 2: Multiply the equation by the integrating factor

Now, multiply both sides of the differential equation by e4xe^{4x}:

e4xy+4e4xy=e4x5x+2e^{4x} y' + 4e^{4x} y = e^{4x} \cdot \frac{5}{x + 2}

This simplifies the left-hand side to the derivative of e4xye^{4x}y:

ddx(e4xy)=e4x5x+2\frac{d}{dx}(e^{4x} y) = e^{4x} \cdot \frac{5}{x + 2}

Step 3: Integrate both sides

Now, integrate both sides with respect to xx:

e4xy=e4x5x+2dxe^{4x} y = \int e^{4x} \cdot \frac{5}{x + 2} \, dx

This integral is non-trivial, and I'll solve it by substitution or other methods.

Let me calculate the integral for the right-hand side.The integral e4x5x+2dx\int e^{4x} \cdot \frac{5}{x + 2} \, dx does not simplify directly using standard methods, so it remains in the form:

e4x5x+2dx=5e4xx+2dx\int e^{4x} \cdot \frac{5}{x + 2} \, dx = 5 \cdot \int \frac{e^{4x}}{x + 2} \, dx

This is a more complex integral, typically requiring advanced techniques or approximation methods, such as integration by parts or using special functions.

Would you like to proceed with numerical methods to approximate the solution, or attempt a series expansion to handle the integral more easily?

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Math Problem Analysis

Mathematical Concepts

Differential Equations
Integrating Factor Method

Formulas

Integrating factor formula: $\mu(x) = e^{\int P(x) dx}$

Theorems

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Suitable Grade Level

Advanced Undergraduate