Question

If x-1/5=5
, then find the value of x^3-1/x^3

Answer 1

x-1/x =5

(x-1/x)^3 =5^3 (a-b)^3=a^3-b^3-3ab(a-b)

x^3-1/x^3-3(x)1/x (x-1/x) =125

x^3-1/x^3-3(5)=125

x^3-1/x^3=125+15

x^3-1/x^3=140