Question
Answer
$$2(3x-i)(3x+i)=-2i^2+18x^2$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}2(3x-i)(3x+i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}(6x-2i)(3x+i) \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}18x^2+6ix-6ix-2i^2 \xlongequal{ } \\[1 em] & \xlongequal{ }18x^2+ \cancel{6ix} -\cancel{6ix}-2i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle3}{\textcircled {3}} } }}}-2i^2+18x^2\end{aligned} $$ | |
| ① | Multiply $ \color{blue}{2} $ by $ \left( 3x-i\right) $ $$ \color{blue}{2} \cdot \left( 3x-i\right) = 6x-2i $$ |
| ② | Multiply each term of $ \left( \color{blue}{6x-2i}\right) $ by each term in $ \left( 3x+i\right) $. $$ \left( \color{blue}{6x-2i}\right) \cdot \left( 3x+i\right) = 18x^2+ \cancel{6ix} -\cancel{6ix}-2i^2 $$ |
| ③ | Combine like terms: $$ 18x^2+ \, \color{blue}{ \cancel{6ix}} \, \, \color{blue}{ -\cancel{6ix}} \,-2i^2 = -2i^2+18x^2 $$ |
This page was created using
Complex Expression calculator