Cauchy-Euler Differential Equation

In summary, the conversation discusses solving the equation x2y''-2xy'+2y=x with boundary conditions y(1)=0, y(2)=0. The approach of treating it as a Cauchy-Euler equation is suggested, and the characteristic equation is found to be r(r-1)-2r+2=0. Solutions using x and x^2 are found, and a particular integral is found using the solution y=Ax ln(x). It is noted that this equation can be reduced to an equation with constant coefficients using a change of variable.
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Homework Statement


Consider the equation x2y''-2xy'+2y=x with bountary conditions y(1)=0, y(2)=0.

I don't know how to solve this without treating it as a Cauchy-Euler equation but I'm struggling because the equation equals x.


The Attempt at a Solution


By treating this as a Cauchy-Euler equation x2y''-2xy'+2y=0 and using y=xr, I get that r=2,1.
I can't find a particular integral for the equation though and I'm not even sure this is a Cauchy-Euler equation anymore.
 
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  • #2
Yes that is a 'Cauchy-Euler' equation and, yes, its characteristic equation is r(r-1)- 2r+ 2=(r- 2)(r- 1)= 0 so that x and [itex]x^2[/itex] are solutions. Since "x" is already a solution, try y= Ax ln(x) as a solution to the entire equation.

That works (and Cauchy-Euler equations are especially easy) because the change of variable [itex]x= e^t[/itex] reduces that equation to the equation with constant coefficients [itex]y''- 3y'+ 2y= e^t[/itex] (the primes now indicate differentiation with respect to t).
 

1. What is a Cauchy-Euler differential equation?

A Cauchy-Euler differential equation is a type of linear, second-order ordinary differential equation that can be written in the form ax²y'' + bxy' + cy = 0, where a, b, and c are constants. It is named after mathematicians Augustin-Louis Cauchy and Leonhard Euler.

2. What is the general solution to a Cauchy-Euler differential equation?

The general solution to a Cauchy-Euler differential equation is y = c₁x^(r₁) + c₂x^(r₂), where r₁ and r₂ are the roots of the characteristic equation ar² + (b-a)r + c = 0. This solution may also include logarithmic or exponential terms depending on the values of r₁ and r₂.

3. How is a Cauchy-Euler differential equation different from a standard second-order differential equation?

A Cauchy-Euler differential equation is different from a standard second-order differential equation in that it contains both x and y terms, while a standard second-order differential equation only contains y terms. This makes solving Cauchy-Euler equations more complex and often requires the use of power series or other special techniques.

4. What is the significance of Cauchy-Euler differential equations in mathematics?

Cauchy-Euler differential equations are important in mathematics because they often arise in physics and engineering problems involving circular motion, vibration, and other physical phenomena. They also have applications in other fields such as signal processing, control theory, and finance.

5. Can Cauchy-Euler differential equations be solved numerically?

Yes, Cauchy-Euler differential equations can be solved numerically using methods such as Euler's method, the Runge-Kutta method, or finite difference methods. However, these methods may not always provide an exact solution and may require additional error analysis to ensure accuracy.

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