Solving a Second-Order Differential Equation with Variable Coefficients

In summary, the person is asking for a hint on how to solve the equation. They don't know how to solve it and are sorry for asking.
  • #1
der.physika
38
0
Solve the Differential Equation [tex]2yy\prime\prime+2xy\prime=0[/tex]

set [tex]p=y\prime[/tex], and then it becomes case 1 in the textbook

Can someone please help me solve this? It's a night mare
 
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  • #2
Doesn't that simplify to y=-x?
 
  • #3
ideasrule said:
Doesn't that simplify to y=-x?

Did you consider the
[tex]y\prime[/tex] that it's not the same as [tex]y[/tex]
 
  • #4
der.physika said:
Did you consider the y' that it's not the same as y
What's your point? y' is a common factor in the equation you wrote. Did you not post the problem correctly?
der.physika said:
Solve the Differential Equation [tex]2yy\prime+2xy\prime=0[/tex]

set [tex]p=y\prime[/tex], and then it becomes case 1 in the textbook
You do realize we don't know what textbook you're using and even less likely to have a copy, right?
 
  • #5
vela said:
What's your point? y' is a common factor in the equation you wrote. Did you not post the problem correctly?

You do realize we don't know what textbook you're using and even less likely to have a copy, right?

Okay, objection 1 makes no sense... but I'll give you you're right for objection 2.

Here's what the textbook says for case 1:

[tex]y\prime=p, y\prime\prime=p\prime\mbox {Dependent variable y missing}[/tex]
 
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  • #6
der.physika said:
Okay, objection 1 makes no sense
Really? You don't see how x=-y is a solution to 2yy'+2xy'=2y'(x+y)=0?
 
  • #7
vela said:
Really? You don't see how x=-y is a solution to 2yy'+2xy'=2y'(x+y)=0?

How did you get that solution besides canceling things out?

Cause, this is like a very annoying class, like what method did you use? Did you use [tex]p\equiv{y}\prime[/tex]
 
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  • #8
You get that solution by canceling things out. It's not the only solution to the original equation, however.
 
  • #9
vela said:
You get that solution by canceling things out. It's not the only solution to the original equation, however.

could you possibly do it, by using the substitution I posted?
 
  • #10
I don't see what that substitution buys you. Also, it's not your textbook's case 1 as y appears in the differential equation.
 
  • #11
ok I posted this wrong, i feel stupid

[tex]2yy\prime\prime+2xy\prime=0[/tex]

how do I solve this?

give me a hint maybe?
 
  • #12
I don't know. Maybe someone else here has a suggestion.
 
  • #13
What's the point of the 2's? I would have just canceled them out from the beginning.

(Y*Y'')/Y' = -X

(Y''/Y')(Y) = -X

Set P = Y', then:

(P'/P)Integral(P) = -X

Ok, I'm sorry. This is going nowhere. Given me 24 hours to think about it.
 

1. What is a differential equation?

A differential equation is a mathematical equation that describes the relationship between a function and its derivatives. It involves the use of derivatives, which represent the rate of change of a function, to model real-world phenomena.

2. What are the types of differential equations?

There are several types of differential equations, including ordinary differential equations, partial differential equations, and stochastic differential equations. Ordinary differential equations involve a single independent variable, while partial differential equations involve multiple independent variables. Stochastic differential equations incorporate random variables into the equation.

3. How are differential equations used in science?

Differential equations are used in various scientific fields, such as physics, engineering, biology, and economics, to model and analyze real-world phenomena. They can be used to understand and predict the behavior of systems and processes, such as population growth, chemical reactions, and fluid flow.

4. What is the order of a differential equation?

The order of a differential equation is determined by the highest derivative present in the equation. For example, a first-order differential equation contains only first derivatives, while a second-order differential equation contains second derivatives.

5. Can all differential equations be solved analytically?

No, not all differential equations can be solved analytically. Some equations may not have a closed-form solution, meaning it cannot be written in terms of familiar mathematical functions. In these cases, numerical methods or approximations may be used to find a solution.

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