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By solving the quadratic equation for <math>\lambda</math>, we will have two eigenvalues <math>\lambda_{1}=-1</math> and <math>\lambda_{2}=-6</math>. By substituting <math>\lambda's</math> into Eq [eq:1]
 
By solving the quadratic equation for <math>\lambda</math>, we will have two eigenvalues <math>\lambda_{1}=-1</math> and <math>\lambda_{2}=-6</math>. By substituting <math>\lambda's</math> into Eq [eq:1]
  
<math>
+
<center><math>
 
\left(A-\lambda_{1}I\right)\vec{x}=\left[\begin{matrix}-5-\lambda_{1} & 2\\
 
\left(A-\lambda_{1}I\right)\vec{x}=\left[\begin{matrix}-5-\lambda_{1} & 2\\
 
2 & -2-\lambda
 
2 & -2-\lambda
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x_{2}
 
x_{2}
 
\end{matrix}\right]=0
 
\end{matrix}\right]=0
+
</math></center>
</math>
+

Revision as of 12:44, 29 April 2014

Let define a n-by-n matrix A and a non-zero vector $ \vec{x}\in\mathbb{R}^{n} $. If there exists a scalar value $ \lambda $ which satisfies the vector equation $ A\vec{x}=\lambda\vec{x} $, we define $ \lambda $ as an eigenvalue of the matrix A, and the corresponding non-zero vector $ \vec{x} $ is called an eigenvector of the matrix A. To determine eigenvalues and eigenvectors a characteristic equation

$ D(\lambda)=det\left(A-\lambda I\right) $

is used. Here is an example of determining eigenvectors and eigenvalues where the matrix A is given by

$ A=\left[\begin{matrix}-5 & 2\\ 2 & -2 \end{matrix}\right] $
.

Then the characteristic equation

$ D(\lambda)=\left(-5-\lambda\right)\left(-2-\lambda\right)-4=\lambda^{2}+7\lambda+6=0. $

By solving the quadratic equation for $ \lambda $, we will have two eigenvalues $ \lambda_{1}=-1 $ and $ \lambda_{2}=-6 $. By substituting $ \lambda's $ into Eq [eq:1]

$ \left(A-\lambda_{1}I\right)\vec{x}=\left[\begin{matrix}-5-\lambda_{1} & 2\\ 2 & -2-\lambda \end{matrix}\right]\left[\begin{matrix}x_{1}\\ x_{2} \end{matrix}\right]=0 $

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