Question

find x^3 +1/x^3
Please do it fast​

Answer 1

x = (3 + 2√2)

1/x = 1/(3 + 2√2)

= (3 - 2√2) / (3 + 2√2)(3 - 2√2)

= (3 - 2√2) / (9-8)

= (3 - 2√2)

so,

x^3 + 1/x^3

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

= (3 + 2√2 + 3 - 2√2 )^3 - 3 (3 + 2√2 + 3 - 2√2 )

= (6)^3 - 3.(6)

= 216 - 18

= 198 (ans.)