A^2=[-1,0,0]
[0,-1,0]
[0,0,1]
A^4=I
B^2012=P^(-1)A^2012*P=p^(-1)*(A^4)^503*P=P^(-1)*P=I
原式=I-2A^2
=[3,0,0]
[0,3,0]
[0,0,-1]