Characteristic equation det(A−λI)=0
∣∣2−λ0111−λ1102−λ∣∣=0
(2−λ)∣∣1−λ102−λ∣∣−∣∣0102−λ∣∣+∣∣011−λ1∣∣=0
(2−λ)2(1−λ)−(1−λ)=0
(1−λ)(4−4λ+λ2−1)=0
(1−λ)2(3−λ)=0
λ1=1,λ2=1,λ3=3 The equation can be written as
λ3−5λ2+7λ−3=0According to Cayley Hamilton theorem, every matrix is the root of it's eigen matrix. Then
A3−5A2+7A−3=0 Given sum
This sum can be written as,
A8−5A7+7A6−3A5
+A4−5A3+8A2−2A+I
=(A3−5A2+7A−3)(A5+A)+(A2+A+I)
Since A3−5A2+7A−3=0, then
A8−5A7+7A6−3A5
+A4−5A3+8A2−2A+I
=A2+A+I
A2=⎣⎡201111102⎦⎤⎣⎡201111102⎦⎤
=⎣⎡4+0+10+0+02+0+22+1+10+1+01+1+22+0+20+0+01+0+4⎦⎤
=⎣⎡504414405⎦⎤
A8−5A7+7A6−3A5
+A4−5A3+8A2−2A+I
=A2+A+I
=⎣⎡504414405⎦⎤+⎣⎡201111102⎦⎤+⎣⎡100010001⎦⎤
=⎣⎡805535508⎦⎤
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