•A 3×3 Example

In[1]:=

A = (2 1 -1) ; 1 2 -1 1 1 0

In[2]:=

p[λ_] = Det[A - λ I _ 3]

Out[2]=

2 - 5 λ + 4 λ^2 - λ^3

In[3]:=

Factor[p[λ]]

Out[3]=

-(-2 + λ) (-1 + λ)^2

In[4]:=

Solve[p[λ] == 0, λ]

Out[4]=

{{λ -> 1}, {λ -> 1}, {λ -> 2}}

Converted by Mathematica  (November 21, 2002)