Question

очень срочно, прошу :3

Answer 1

3) =(n^3(n +1) -(n+1)) /(1-n²) =

=(n +1)(n^3 -1) /(-(n -1)(n+1) =

= -(n -1)(n² +n +1) /(n -1) =

= -(n² +n +1)