I want to use the power method to find the largest root of a

I want to use the power method to find the largest root of a polynomial. To do this, I think that I need to compute the companion matrix of the polynomial, but I\'m not sure how to do that. Please explain using the following example, or let me know if I\'m approaching the problem wrong.

EX: 5+pi*x+9*x^2+9*pi*x^3+x^4.

Thank you for the help