Tap the blue circles to see an explanation.
$$ \begin{aligned}6+9i-(-3-i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}6+9i+3+i \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}10i+9\end{aligned} $$ | |
① | Remove the parentheses by changing the sign of each term within them. $$ - \left( -3-i \right) = 3+i $$ |
② | Combine like terms: $$ \color{blue}{6} + \color{red}{9i} + \color{blue}{3} + \color{red}{i} = \color{red}{10i} + \color{blue}{9} $$ |