$$ \begin{aligned}(p-1)^2& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}p^2-2p+1\end{aligned} $$ | |
① | Find $ \left(p-1\right)^2 $ using formula. $$ (A - B)^2 = \color{blue}{A^2} - 2 \cdot A \cdot B + \color{red}{B^2} $$where $ A = \color{blue}{ p } $ and $ B = \color{red}{ 1 }$. $$ \begin{aligned}\left(p-1\right)^2 = \color{blue}{p^2} -2 \cdot p \cdot 1 + \color{red}{1^2} = p^2-2p+1\end{aligned} $$ |