Tap the blue circles to see an explanation.
| $$ \begin{aligned}(x-12y)(x+3y)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}x^2+3xy-12xy-36y^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}x^2-9xy-36y^2\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{x-12y}\right) $ by each term in $ \left( x+3y\right) $. $$ \left( \color{blue}{x-12y}\right) \cdot \left( x+3y\right) = x^2+3xy-12xy-36y^2 $$ |
| ② | Combine like terms: $$ x^2+ \color{blue}{3xy} \color{blue}{-12xy} -36y^2 = x^2 \color{blue}{-9xy} -36y^2 $$ |