Tap the blue circles to see an explanation.
| $$ \begin{aligned}(x-1)(x+x^8)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}x^2+x^9-x-x^8 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}x^9-x^8+x^2-x\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{x-1}\right) $ by each term in $ \left( x+x^8\right) $. $$ \left( \color{blue}{x-1}\right) \cdot \left( x+x^8\right) = x^2+x^9-x-x^8 $$ |
| ② | Combine like terms: $$ x^9-x^8+x^2-x = x^9-x^8+x^2-x $$ |