Another partial differential equation problem

In summary, the given problem involves finding the general solution of an equation by using a change of variables. The equations used for this include du/dx and du/dt, which can be expressed in terms of du/d(alpha) and du/d(beta). The book suggests using alpha=x+2t and beta=x, but it is unclear how to determine these variables.
  • #1
pentazoid
146
0

Homework Statement



Derived the general solution of the given equation by using an appropriate change of variables
5.) du/dt-2(du/dx)=2

Homework Equations



du/dx=du/d(alpha)*d(alpha)/dx+du/d(beta)*d(beta)/dx
du/dt= du/d(alpha)*d(alpha)/dt+du/d(beta)*d(beta)/dt

The Attempt at a Solution



not really sure how to determine du/d(alpha),d(alpha)/dx,d(beta)/dx ,d(alpha)/dt,d(beta)/dt

book says alpha=x+2t, beta=x
 
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  • #2
pentazoid said:

Homework Statement



Derived the general solution of the given equation by using an appropriate change of variables
5.) du/dt-2(du/dx)=2

Homework Equations



du/dx=du/d(alpha)*d(alpha)/dx+du/d(beta)*d(beta)/dx
du/dt= du/d(alpha)*d(alpha)/dt+du/d(beta)*d(beta)/dt

The Attempt at a Solution



not really sure how to determine du/d(alpha),d(alpha)/dx,d(beta)/dx ,d(alpha)/dt,d(beta)/dt

book says alpha=x+2t, beta=x
[tex]
\frac{\partial\alpha}{\partial x}=1,\frac{\partial\beta}{\partial x}=1 so
\[
\frac{\partial u}{\partial x}=\frac{\partial u}{\partial\alpha}\frac{\partial\alpha}{\partial x}+\frac{\partial u}{\partial\beta}\frac{\partial\beta}
{\partial x}=\frac{\partialu}{\partialx}=\frac{\partial u}{\partial\alpha}+\frac{\partial u}{\partial\beta}
\]
[/tex]
did that help?
 
  • #3
the1ceman said:
[tex]
\frac{\partial\alpha}{\partial x}=1,\frac{\partial\beta}{\partial x}=1 so
\[
\frac{\partial u}{\partial x}=\frac{\partial u}{\partial\alpha}\frac{\partial\alpha}{\partial x}+\frac{\partial u}{\partial\beta}\frac{\partial\beta}
{\partial x}=\frac{\partialu}{\partialx}=\frac{\partial u}{\partial\alpha}+\frac{\partial u}{\partial\beta}
\]
[/tex]
did that help?

I probably should have said in the back of the book, they give you alpha and beta. They don't give you the equations for alpha and beta in the problem. I don't understand how to determine alpha and beta.
 

1. What is a partial differential equation?

A partial differential equation (PDE) is a mathematical equation that involves partial derivatives of an unknown function with respect to multiple independent variables. It describes the relationship between the function and its derivatives in a particular system.

2. How is a partial differential equation different from an ordinary differential equation?

A partial differential equation involves partial derivatives with respect to multiple independent variables, while an ordinary differential equation involves derivatives with respect to a single independent variable. PDEs are commonly used to model physical phenomena in multiple dimensions, while ODEs are used for single-dimensional problems.

3. What are some applications of partial differential equations?

Partial differential equations have a wide range of applications in various fields such as physics, engineering, economics, and biology. They are commonly used to model phenomena such as heat transfer, fluid dynamics, electromagnetism, and quantum mechanics.

4. How are partial differential equations solved?

There is no general method for solving all types of partial differential equations. The approach to solving a PDE depends on its type and specific form. Some common techniques include separation of variables, method of characteristics, and numerical methods such as finite difference or finite element methods.

5. Are partial differential equations important in modern science?

Yes, partial differential equations are crucial in modern science and have been instrumental in many scientific discoveries and technological advancements. They are used to model complex systems and make predictions about the behavior of physical phenomena, making them essential tools for scientists and engineers.

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