Question

If x-1/x=5 determine the value of x^2+1/x^2 and x^3-1/x^3 without solving the original equation.

It may seem obvious but as my username says, I'm not very bright. Thanks in advance. :)

Answer 1

Writing x^2+1/x^2 as (x-1/x)^2+2 & writing x^3-1/x^3 as (x-1/x)^3+3(x-1/x) gives us the solution of former as 27 and later as 140.

Answer 2

Thanks man! :D