There may be a better way but I started by expanding it all out and simplify
Taking it to one side and put equal to 0
After you do that and present your answer here I will help you more.
n3= n3-1+n3-8+n3-27
n3=n3+n3+n3-1-8-27
n3=3n3-9-27
n3=3n3-18
-n3+n3=-18/3
6 (ans)
Expanding a little bit on Melody's answer...
You expand and get \(n^3 = (n^3-3n^2-3n+1)+(n^3-6n^2+12n+8)+(n^3-9n^2+27n-27)\).
Solve from here.