Give :

\(P=\dfrac{x^7+x^6+x^5+x^4+x^3+x^2+x+1}{x^4-1}\)

a) Compact P.

b) Calculate P when x = 2 ?

Solve the expression (calculator acceptable): 

\(\left\{{}\begin{matrix}x+y+z=10\\xy+yz+zx=31\\xyz=30\end{matrix}\right.\)