Tap the blue circles to see an explanation.
| $$ \begin{aligned}(4x-7)(4x+7)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}16x^2+28x-28x-49 \xlongequal{ } \\[1 em] & \xlongequal{ }16x^2+ \cancel{28x} -\cancel{28x}-49 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}16x^2-49\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{4x-7}\right) $ by each term in $ \left( 4x+7\right) $. $$ \left( \color{blue}{4x-7}\right) \cdot \left( 4x+7\right) = 16x^2+ \cancel{28x} -\cancel{28x}-49 $$ |
| ② | Combine like terms: $$ 16x^2+ \, \color{blue}{ \cancel{28x}} \, \, \color{blue}{ -\cancel{28x}} \,-49 = 16x^2-49 $$ |