Question

if x+1/x = 7,calculate the value of x3+1/x3

Answer 1

x+1/x = 7
x+1 = 7x
6x = 1
x =1/6

I assumed that by x3 you means x^3

x^3 = (1/6)^3 = 1/216

x^3+1/x^3 = (1/216 + 216/216)/ 1/216
                 = 217/216 * 216/1
                   = 217

Answer 2

from the 1st equation , we get the value of x = 1/6
putting the value of x as 1/6 in 2nd equation , 
we get-

(1/6)3 + 1 / (1/6) 3 = 217

answer = 217.