x+1/x =3 (x+1/x)^3 =27 x^3+1/x^3 + 3(x+1/x) = 27 x^3+1/x^3 = 18 (x+1/x)^5 = 243 x^5+1/x^5 + 5(x^3+1/x^3)+10(x+1/x) =243 x^5+1/x^5 =243-90-30 =123
