Question

If x+1/x =3 whole 1/3, find the value of x3-1/x3​

Answer 1

x+1/x=3

doing cube both side

(x+1/x^3)3=3^3

=x^3+1/x^3+3x . 1/x .x+1/x=27 [ (a+b)^3=a^3+b^3 +3ab(a+b)]

=x^3 +1/x^3 +3(3)=27 (coz x+1/x=3)

=x^3 +1/x^3=27-9

=18