Question
Answer
$$(a-2)(a+2)=a^2-4$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(a-2)(a+2)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}a^2+2a-2a-4 \xlongequal{ } \\[1 em] & \xlongequal{ }a^2+ \cancel{2a} -\cancel{2a}-4 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}a^2-4\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{a-2}\right) $ by each term in $ \left( a+2\right) $. $$ \left( \color{blue}{a-2}\right) \cdot \left( a+2\right) = a^2+ \cancel{2a} -\cancel{2a}-4 $$ |
| ② | Combine like terms: $$ a^2+ \, \color{blue}{ \cancel{2a}} \, \, \color{blue}{ -\cancel{2a}} \,-4 = a^2-4 $$ |
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