Question
Answer
$$(-4+5i)\cdot(-4-5i)=-25i^2+16$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(-4+5i)\cdot(-4-5i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}16+20i-20i-25i^2 \xlongequal{ } \\[1 em] & \xlongequal{ }16+ \cancel{20i} -\cancel{20i}-25i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-25i^2+16\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{-4+5i}\right) $ by each term in $ \left( -4-5i\right) $. $$ \left( \color{blue}{-4+5i}\right) \cdot \left( -4-5i\right) = 16+ \cancel{20i} -\cancel{20i}-25i^2 $$ |
| ② | Combine like terms: $$ 16+ \, \color{blue}{ \cancel{20i}} \, \, \color{blue}{ -\cancel{20i}} \,-25i^2 = -25i^2+16 $$ |
This page was created using
Complex Expression calculator