2 z + 6*z + 1
z^2 + 6*z + 1
/ ___\ / ___\ \x + 3 + 2*\/ 2 /*\x + 3 - 2*\/ 2 /
(x + 3 + 2*sqrt(2))*(x + 3 - 2*sqrt(2))
2 1 + z + 6*z
1 + z^2 + 6*z
1 + z*(6 + z)
1.0 + z^2 + 6.0*z