Tap the blue circles to see an explanation.
$$ \begin{aligned}-4(x+1)^3& \xlongequal{ }-4(x^3+3x^2+3x+1) \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-(4x^3+12x^2+12x+4) \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-4x^3-12x^2-12x-4\end{aligned} $$ | |
① | Multiply $ \color{blue}{4} $ by $ \left( x^3+3x^2+3x+1\right) $ $$ \color{blue}{4} \cdot \left( x^3+3x^2+3x+1\right) = 4x^3+12x^2+12x+4 $$ |
② | Remove the parentheses by changing the sign of each term within them. $$ - \left(4x^3+12x^2+12x+4 \right) = -4x^3-12x^2-12x-4 $$ |