Question about using matrices for differential equations

In summary, the conversation was about finding the general solution to a system of differential equations with given initial values. The expert summarizes the steps taken and the confusion about the coefficients. The conversation also touches on the topic of systems of differential equations and the book being used in the course.
  • #1
EtherNohow
4
0
Let x(t)=
[x1(t)
x2(t)]
be a solution to the system of differential equations:

x′1(t)=−2x1(t)+2x2(t)
x′2(t)==−6x1(t)+9x2(t)

If x(0)=
[4
-2]
find x(t).

I got the eigenvalues to be -6 and -5, but I don't know how to calculate the coefficients in front of the exponents. For lambda=-6 I get the vector (1, -2) and for lambda=-5 I get the vector (2, -3). I think these would be the coefficients, but I'm not sure, and I don't know how to use the initial values for x(0). Thanks for your help!
 
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  • #2
Given a system of equations ##\dot{\mathbf{x}}(t) = A \mathbf{x}(t)##, what is the general solution of this problem?
 
  • #3
micromass said:
Given a system of equations ##\dot{\mathbf{x}}(t) = A \mathbf{x}(t)##, what is the general solution of this problem?
I put the vectors eigenvectors from into a matrix and put 4 and -2 on the right and solved for the two variables. I got -8 and 6 but the website says only -8 is right, and in don't know where to get the other two coefficients?
 
  • #4
That doesn't answer my question at all.
 
  • #5
micromass said:
That doesn't answer my question at all.
Wouldn't it just be A? Since other than that both sides are the same?
 
  • #6
In your course, what does it tell you about systems of differential equations? What book are you reading?
 
  • #7
micromass said:
In your course, what does it tell you about systems of differential equations? What book are you reading?
I haven't taken differential equations yet. I'm in matrix algebra using Elementary Linear Algebra 7e by Larson.
 

FAQ: Question about using matrices for differential equations

1. What are matrices used for in solving differential equations?

Matrices are used to represent and solve systems of linear equations, which are often used to describe differential equations. Matrices can help simplify the process of solving these equations, and can also be used to find solutions for higher-order differential equations.

2. How do matrices help with solving differential equations?

Matrices allow us to perform operations on multiple equations simultaneously, which can be very helpful when solving systems of differential equations. They also allow us to manipulate the equations in various ways, such as row operations, to make them easier to solve.

3. Can matrices be used to solve any type of differential equation?

No, matrices are most commonly used to solve linear differential equations. However, they can also be used to solve some nonlinear differential equations, depending on the specific situation.

4. Are there any limitations to using matrices for solving differential equations?

While matrices can be a powerful tool in solving differential equations, they do have some limitations. For example, they may not be able to handle certain types of differential equations, such as those with discontinuous or non-differentiable functions.

5. Can I use matrices to solve differential equations by hand?

Yes, it is possible to use matrices to solve differential equations by hand, but it may be more time-consuming and complex compared to using a computer program or calculator. It is important to have a strong understanding of matrix operations and differential equations in order to successfully solve them by hand.

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