Question

Find all of the eigenvalues λ of the matrix A. (Hint: Use the method of Example 4.5 of finding the solutions to the equation 0 = det(A − λI). Enter your answers as a comma-separated list.) A = 3 5 8 0

Answer 1

Answer:

$\lambda=8,\ \lambda=-5$

Step-by-step explanation:

Eigenvalues of a Matrix

Given a matrix A, the eigenvalues of A, called $\lambda$ are scalars who comply with the relation:

$det(A-\lambda I)=0$

Where I is the identity matrix

$I=\left[\begin{array}{cc}1&0\\0&1\end{array}\right]$

The matrix is given as

$A=\left[\begin{array}{cc}3&5\\8&0\end{array}\right]$

Set up the equation to solve

$det\left(\left[\begin{array}{cc}3&5\\8&0\end{array}\right]-\left[\begin{array}{cc}\lambda&0\\0&\lambda \end{array}\right]\right)=0$

Expanding the determinant

$det\left(\left[\begin{array}{cc}3-\lambda&5\\8&-\lambda\end{array}\right]\right)=0$

$(3-\lambda)(-\lambda)-40=0$

Operating Rearranging

$\lambda^2-3\lambda-40=0$

Factoring

$(\lambda-8)(\lambda+5)=0$

Solving, we have the eigenvalues

$\boxed{\lambda=8,\ \lambda=-5}$