[tex](1-2n)^3-7n(n^2-2)[/tex][tex]\begin{gathered} (1-2n)(1-2n)(1-2n)-7n(n^2-2) \\ (1-2n)(1-2n-2n+4n^2)-7n^3+14n \\ (1-2n)(1-4n+4n^2)-7n^3+14n \\ 1-4n+4n^2-2n+8n^2-8n^3-7n^3+14n \end{gathered}[/tex]
Collect like-terms, we have:
[tex]\begin{gathered} -8n^3-7n^3+4n^2+8n^2-4n-2n+14n+1 \\ \Rightarrow-15n^3+12n^2+8n+1 \end{gathered}[/tex]
