Solution
A∈M6(R)⟹deg(Pλ)
we have A3−4A2+3A=0
⟺A(A2−4A+3I)=0
⟺(A−I)(A−3I)=0
Let f(λ)=(λ−I)(λ−3I) Then f(A)=0
⟹P(λ)=(λ−1)n1(λ−3)n2where n1+n2=6(1)
we have tr(A)=8⟺n1(1)+n2(3)=8 ⟺n1+3n2=8
from.(1) {n1+n2=6n1+3n2=8⟹2n2=2⟹n2=1,n1=5
Answer
Therefore. P(λ)=(λ−1)5(λ−3)