Because: x- 1/x=3, so: (x- 1/x) 2 = 9.

( 1)x^2-2+ 1/x^2=9

So: x 2+1/x 2 =11.

We can get: x+ 1/x= root number 13.

(2)x^3+ 1/x^3=(x+ 1/x)^3-3(x+ 1/x)

= (root 13) 3-3 root 13= 10 root 13

(3)x^4+ 1/x^4=(x^2+ 1/x^2)^2-2

= 1 1^2- 1= 1 19