Find Eigenvalues without function "eig"

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Jaycie Bishop
Jaycie Bishop 2020-10-11
编辑： KSSV 2020-10-12
I performed this by hand and know that the eigenvalues are 10, -1, and 4. But clearly that's not what I got... Any help would be nice.

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回答（2 个）

KSSV
KSSV 2020-10-11
编辑：KSSV 2020-10-12
syms x
A = [10 0 0; 1 -3 -7 ; 0 2 6] ;
p = det(A-eye(3)*x) % this is the characteristic equation
val = solve(p) % solve this for roots
The polynomial equation, you get is:
poly =
Using roots:
p = [-1 13 -26 -40] ;
val = roots(p)
Paul
Paul 2020-10-11
roots(poly(A))
Though I’m sure one could come with an A for which this approach will fail due to numerical accuracy issues. In which case converting A to a syms object as in another answer may be preferred.

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