Question

If x² +1/x=7 find x³+1/x³

Answer 1

(x + 1/x)2 = x2 + 1/x2 + 2
(x + 1/x)2 = 9
x + 1/x = 3

now
(x + 1/x)3 = x3 + 1/x3 + 3(x + 1/x)
27 = x3 + 1/x3 + 9
or
x3 + 1/x3 = 27 - 9 = 18
it should be the answer

Answer 2

18 is your Answer...!!