Question
Answer
$$(2c-3)(2c+3)=4c^2-9$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(2c-3)(2c+3)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}4c^2+6c-6c-9 \xlongequal{ } \\[1 em] & \xlongequal{ }4c^2+ \cancel{6c} -\cancel{6c}-9 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}4c^2-9\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{2c-3}\right) $ by each term in $ \left( 2c+3\right) $. $$ \left( \color{blue}{2c-3}\right) \cdot \left( 2c+3\right) = 4c^2+ \cancel{6c} -\cancel{6c}-9 $$ |
| ② | Combine like terms: $$ 4c^2+ \, \color{blue}{ \cancel{6c}} \, \, \color{blue}{ -\cancel{6c}} \,-9 = 4c^2-9 $$ |
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