The Method of Elimination: x" = 6x + 2y, y" = 3x + 7y

bearej50

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FIND THE GENERAL SOLUTION OF THE LINEAR SYSTEM

x'' = 6x + 2y, y'' = 3x + 7y
 
Re: The Method of Elimination

bearej50 said:
FIND THE GENERAL SOLUTION OF THE LINEAR SYSTEM

x'' = 6x + 2y, y'' = 3x + 7y

What have you tried?

I'd suggest trying trial solutions x=exp(lambda t), y = exp(mu t), then get some equations for lambda and mu.
 
Re: The Method of Elimination

bearej50 said:
FIND THE GENERAL SOLUTION OF THE LINEAR SYSTEM

x'' = 6x + 2y, y'' = 3x + 7y

Alternatively, noting the title of your post...

The method of elimination involves rearranging the equations to eliminate one of the variables.

For example, the first equation can be used to find y in terms of x and x''. Then you can substitute this into the second equation to get an equation just involving x, x'' and x''''.
 
One way to solve a system like this is to, first, find the characteristic polynomial.

\(\displaystyle det(A-{\lambda}I)=\begin{vmatrix}6-{\lambda}&2\\3&7-{\lambda}\end{vmatrix}\)

\(\displaystyle {\lambda}^{2}-13{\lambda}+36=0, \;\ {\lambda}=4, \;\ {\lambda}=9\)

4 and 9 are the eigenvalues.

Now, use these in the original system to find the related eigenvectors.

Have you seen this method before?.
 
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