Question

x+1/x=7,find x3-1/x3

Answer 1

(x + 1)/x = 7
x + 1 = 7x
6x = 1
x = 1/6.

(3x - 1)/3x = [{(3 * 1/6)} - 1] / 3 * 1/6
= (1/2 - 1) / 1/2
= (-1/2) / (1/2)
= -1