Question

x2+1/x2=7 find x3+1/x3 and x-1/"x

Answer 1

x2+ 1/x2 = 7
on adding 2 on both sides
x2+1/x2 +2 = 7+2=9
{x+1/x}2 = 9
x+1/x = 3
on cubing both side
x3+1/x3 + 3(x+1/x) = 27
x3 +1/x3 + 3(3) = 27
x3 +1/x3 = 27-9 = 18