Question
Answer
$$(6x-5i)(6x+5i)=-25i^2+36x^2$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(6x-5i)(6x+5i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}36x^2+30ix-30ix-25i^2 \xlongequal{ } \\[1 em] & \xlongequal{ }36x^2+ \cancel{30ix} -\cancel{30ix}-25i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-25i^2+36x^2\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{6x-5i}\right) $ by each term in $ \left( 6x+5i\right) $. $$ \left( \color{blue}{6x-5i}\right) \cdot \left( 6x+5i\right) = 36x^2+ \cancel{30ix} -\cancel{30ix}-25i^2 $$ |
| ② | Combine like terms: $$ 36x^2+ \, \color{blue}{ \cancel{30ix}} \, \, \color{blue}{ -\cancel{30ix}} \,-25i^2 = -25i^2+36x^2 $$ |
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