#page 260
a=matrix(QQ,[[0.4,0,0.1],[0,0.1,0.8],[0.5,0.7,0.1]])
i=matrix(QQ,[[1,0,0],[0,1,0],[0,0,1]])
x2=matrix(QQ,[1,5,5])
x1=transpose(x2)
x=i-a
p=x.inverse()
p*x1