Question

the 2nd one pls help me

Answer 1

X+ 1/x = 9

Taking cube on both sides,

(x+ 1/x)^3 = 729

now expanding using
(a+b)^3= a^3 + b^3 + 3ab(a+b)

we get, x^3 + (1/x)^3 = 702.