Answer
$$(11+7i)\cdot(-1+7i)=49i^2+70i-11$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(11+7i)\cdot(-1+7i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-11+77i-7i+49i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}49i^2+70i-11\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{11+7i}\right) $ by each term in $ \left( -1+7i\right) $. $$ \left( \color{blue}{11+7i}\right) \cdot \left( -1+7i\right) = -11+77i-7i+49i^2 $$ |
| ② | Combine like terms: $$ -11+ \color{blue}{77i} \color{blue}{-7i} +49i^2 = 49i^2+ \color{blue}{70i} -11 $$ |
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