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