Tap the blue circles to see an explanation.
| $$ \begin{aligned}(n^3+9)(n+1)^3& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}(n^3+9)(1n^3+3n^2+3n+1) \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} \htmlClass{explanationCircle explanationCircle3}{\textcircled {3}} } }}}n^6+3n^5+3n^4+10n^3+27n^2+27n+9\end{aligned} $$ | |
| ① | Find $ \left(n+1\right)^3 $ using formula $$ (A + B) = A^3 + 3A^2B + 3AB^2 + B^3 $$where $ A = n $ and $ B = 1 $. $$ \left(n+1\right)^3 = n^3+3 \cdot n^2 \cdot 1 + 3 \cdot n \cdot 1^2+1^3 = n^3+3n^2+3n+1 $$ |
| ② | Multiply each term of $ \left( \color{blue}{n^3+9}\right) $ by each term in $ \left( n^3+3n^2+3n+1\right) $. $$ \left( \color{blue}{n^3+9}\right) \cdot \left( n^3+3n^2+3n+1\right) = n^6+3n^5+3n^4+n^3+9n^3+27n^2+27n+9 $$ |
| ③ | Combine like terms: $$ n^6+3n^5+3n^4+ \color{blue}{n^3} + \color{blue}{9n^3} +27n^2+27n+9 = n^6+3n^5+3n^4+ \color{blue}{10n^3} +27n^2+27n+9 $$ |