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