Courtesy of Heureka :)
\(\begin{array}{|rcll|} \hline && \mathbf{(t-1)^3 + 6(t-1)^2 + 12(t-1) + 8 } \\ &=& (t-1)^3 + 3(t-1)^2+3(t-1) +1 \\ && \quad + 3(t-1)^2+9(t-1)+7 \\ &=& t^3 + 3(t-1)^2+9(t-1)+7 \\ &=& t^3 + 3(t^2-2t+1)+9t-9+7 \\ &=& t^3 + 3t^2-6t+3+9t-9+7 \\ &=& t^3 + 3t^2+3t+1 \quad & | \quad (1+t)^3 = t^3+3t^2+3t+1 \\ &\mathbf{=}& \mathbf{(1+t)^3} \\ \hline \end{array}\)
\begin{array}{|rcll|} \hline && \mathbf{(t-1)^3 + 6(t-1)^2 + 12(t-1) + 8 } \\
&=& (t-1)^3 + 3(t-1)^2+3(t-1) +1\\
&& \quad + 3(t-1)^2+9(t-1)+7 \\
&=& t^3 + 3(t-1)^2+9(t-1)+7 \\
&=& t^3 + 3(t^2-2t+1)+9t-9+7 \\
&=& t^3 + 3t^2-6t+3+9t-9+7 \\
&=& t^3 + 3t^2+3t+1 \quad & | \quad (1+t)^3 = t^3+3t^2+3t+1\\
&\mathbf{=}& \mathbf{(1+t)^3} \\
\hline \end{array}