(x^2+3xy+y^2)dx-x^2dy=0

4 min read Jul 03, 2024
(x^2+3xy+y^2)dx-x^2dy=0

Differential Equation: (x^2+3xy+y^2)dx-x^2dy=0

In this article, we will discuss the differential equation (x^2+3xy+y^2)dx-x^2dy=0 and its solution.

Form of the Differential Equation

The given differential equation is of the form:

M(x,y)dx+N(x,y)dy=0

where M(x,y)=x^2+3xy+y^2 and N(x,y)=-x^2.

Solution of the Differential Equation

To solve this differential equation, we can use an integrating factor. Let's find the integrating factor:

μ(x,y)=e^∫(N_x-M_y)/M dx

where N_x is the partial derivative of N with respect to x, and M_y is the partial derivative of M with respect to y.

First, let's find the partial derivatives:

N_x=-2x M_y=3x+2y

Now, we can find the integrating factor:

μ(x,y)=e^∫(-2x-(3x+2y))/(x^2+3xy+y^2) dx

μ(x,y)=1/(x^2+3xy+y^2)

Now, multiply the original differential equation by the integrating factor:

(1/(x^2+3xy+y^2))(x^2+3xy+y^2)dx-(1/(x^2+3xy+y^2))x^2dy=0

This simplifies to:

dx-(x^2/(x^2+3xy+y^2))dy=0

Solving the Differential Equation

To solve this differential equation, we can integrate both sides with respect to x, treating y as a constant:

∫dx-∫(x^2/(x^2+3xy+y^2))dy=C

where C is the constant of integration.

The first integral is simple:

x=C1

The second integral is more complicated:

-∫(x^2/(x^2+3xy+y^2))dy=C2

To evaluate this integral, we can use the substitution u=x^2+3xy+y^2, du=(2x+3y)dx. Then, the integral becomes:

-∫(1/u)du=C2

which evaluates to:

ln|x^2+3xy+y^2|=C2

Now, we can combine the two results:

x-C ln|x^2+3xy+y^2|=C

which is the general solution of the differential equation.

Conclusion

In this article, we have solved the differential equation (x^2+3xy+y^2)dx-x^2dy=0 using an integrating factor. The general solution of the differential equation is x-C ln|x^2+3xy+y^2|=C, where C is the constant of integration.

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