Initial Value Problem for a System of Linear Differential Equations

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SUMMARY

The discussion centers on solving an initial value problem for a system of linear differential equations represented by the equations \(x' = \frac{1}{2}(45 - x) + \frac{1}{4}(y - x)\), \(y' = \frac{1}{4}(x - y) + \frac{1}{2}(35 - y) + \frac{1}{2}(z - y) + 20\), and \(z' = \frac{1}{2}(y - z) + \frac{1}{2}(35 - z)\). Participants agree that the solution involves diagonalizing the coefficient matrix and decoupling the equations. The final solution is expressed in terms of the eigenvalues and eigenvectors of the matrix, leading to explicit functions for \(x\), \(y\), and \(z\) based on initial conditions.

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  • Understanding of linear differential equations
  • Familiarity with matrix diagonalization
  • Knowledge of eigenvalues and eigenvectors
  • Proficiency in solving initial value problems
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  • Study the process of diagonalizing matrices in linear algebra
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Mathematicians, engineers, and students specializing in differential equations, particularly those working on systems of linear equations and initial value problems.

  • #31
We have

$$A=\begin{pmatrix}-(m_0+m_1) & m_1 & 0 \\ m_1 & -(m_1+m_2+m_3) & m_3 \\ 0 & m_3 & -(m_3+m_4)\end{pmatrix}$$

$$C=\begin{pmatrix}45m_0\\20\\35m_4\end{pmatrix}$$

So, we have to solve $X=-A^{-1}C$ subject to $z>x$, right?? (Wondering)

- - - Updated - - -

I like Serena said:
I believe you're supposed to find the solution for $X = X(t)$, which contains factors $e^{\lambda t}$.
Those terms with $e^{\lambda t}$ will not and cannot be zero. (Wasntme)

We will get three relations of the form $e^{\lambda t}=0$, right?? What does this mean?? (Wondering)
 
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  • #32
mathmari said:
We have

$$A=\begin{pmatrix}-(m_0+m_1) & m_1 & 0 \\ m_1 & -(m_1+m_2+m_3) & m_3 \\ 0 & m_3 & -(m_3+m_4)\end{pmatrix}$$

$$C=\begin{pmatrix}45m_0\\20\\35m_4\end{pmatrix}$$

So, we have to solve $X=-A^{-1}C$ subject to $z>x$, right?? (Wondering)

Yep. (Smile)

- - - Updated - - -

We will get three relations of the form $e^{\lambda t}=0$, right?? What does this mean?? (Wondering)

I'm not so sure that's what we will get. How did you get it? (Wondering)
If we would, there would be no solution. (Wasntme)
 
  • #33
I like Serena said:
Yep. (Smile)

How can we find the inverse of $A$?? I got stuck right now...
 
  • #34
I like Serena said:
I'm not so sure that's what we will get. How did you get it? (Wondering)
If we would, there would be no solution. (Wasntme)

$\lambda$ is negative... So, that means that $t \rightarrow +\infty$, or not?? (Wondering)
 
  • #35
mathmari said:
$\lambda$ is negative... So, that means that $t \rightarrow +\infty$, or not?? (Wondering)

If $e^{\lambda t} = 0$. What is the reason you think it is? (Wondering)
 
  • #36
mathmari said:
How can we find the inverse of $A$?? I got stuck right now...

I'm not quite clear on the problem.
Aren't all $m_i$ values given? (Wondering)
Wouldn't it only be $m_1$ that we make variable?
 

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