Tap the blue circles to see an explanation.
$$ \begin{aligned}(4-2i)\cdot(1-2i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}4-8i-2i+4i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}4i^2-10i+4\end{aligned} $$ | |
① | Multiply each term of $ \left( \color{blue}{4-2i}\right) $ by each term in $ \left( 1-2i\right) $. $$ \left( \color{blue}{4-2i}\right) \cdot \left( 1-2i\right) = 4-8i-2i+4i^2 $$ |
② | Combine like terms: $$ 4 \color{blue}{-8i} \color{blue}{-2i} +4i^2 = 4i^2 \color{blue}{-10i} +4 $$ |