Question
Answer
$$-2+9i-3\cdot(7-8i)=33i-23$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}-2+9i-3\cdot(7-8i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-2+9i-(21-24i) \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-2+9i-21+24i \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle3}{\textcircled {3}} } }}}33i-23\end{aligned} $$ | |
| ① | Multiply $ \color{blue}{3} $ by $ \left( 7-8i\right) $ $$ \color{blue}{3} \cdot \left( 7-8i\right) = 21-24i $$ |
| ② | Remove the parentheses by changing the sign of each term within them. $$ - \left( 21-24i \right) = -21+24i $$ |
| ③ | Combine like terms: $$ \color{blue}{-2} + \color{red}{9i} \color{blue}{-21} + \color{red}{24i} = \color{red}{33i} \color{blue}{-23} $$ |
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