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