Tap the blue circles to see an explanation.
$$ \begin{aligned}(x-4)(x+1)(x-2)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}(x^2+x-4x-4)(x-2) \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}(x^2-3x-4)(x-2) \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle3}{\textcircled {3}} } }}}x^3-2x^2-3x^2+6x-4x+8 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle4}{\textcircled {4}} } }}}x^3-5x^2+2x+8\end{aligned} $$ | |
① | Multiply each term of $ \left( \color{blue}{x-4}\right) $ by each term in $ \left( x+1\right) $. $$ \left( \color{blue}{x-4}\right) \cdot \left( x+1\right) = x^2+x-4x-4 $$ |
② | Combine like terms: $$ x^2+ \color{blue}{x} \color{blue}{-4x} -4 = x^2 \color{blue}{-3x} -4 $$ |
③ | Multiply each term of $ \left( \color{blue}{x^2-3x-4}\right) $ by each term in $ \left( x-2\right) $. $$ \left( \color{blue}{x^2-3x-4}\right) \cdot \left( x-2\right) = x^3-2x^2-3x^2+6x-4x+8 $$ |
④ | Combine like terms: $$ x^3 \color{blue}{-2x^2} \color{blue}{-3x^2} + \color{red}{6x} \color{red}{-4x} +8 = x^3 \color{blue}{-5x^2} + \color{red}{2x} +8 $$ |