Question
Answer
$$(-8i-7)(-8i+7)=64i^2-49$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(-8i-7)(-8i+7)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}64i^2-56i+56i-49 \xlongequal{ } \\[1 em] & \xlongequal{ }64i^2 -\cancel{56i}+ \cancel{56i}-49 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}64i^2-49\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{-8i-7}\right) $ by each term in $ \left( -8i+7\right) $. $$ \left( \color{blue}{-8i-7}\right) \cdot \left( -8i+7\right) = 64i^2 -\cancel{56i}+ \cancel{56i}-49 $$ |
| ② | Combine like terms: $$ 64i^2 \, \color{blue}{ -\cancel{56i}} \,+ \, \color{blue}{ \cancel{56i}} \,-49 = 64i^2-49 $$ |
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