Question
Answer
$$(5-5i)\cdot(3+3i)=-15i^2+15$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(5-5i)\cdot(3+3i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}15+15i-15i-15i^2 \xlongequal{ } \\[1 em] & \xlongequal{ }15+ \cancel{15i} -\cancel{15i}-15i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-15i^2+15\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{5-5i}\right) $ by each term in $ \left( 3+3i\right) $. $$ \left( \color{blue}{5-5i}\right) \cdot \left( 3+3i\right) = 15+ \cancel{15i} -\cancel{15i}-15i^2 $$ |
| ② | Combine like terms: $$ 15+ \, \color{blue}{ \cancel{15i}} \, \, \color{blue}{ -\cancel{15i}} \,-15i^2 = -15i^2+15 $$ |
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