Question

If x2+1/x2 = 7 find the value of 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 shoul be the answer