$$ \begin{aligned}(3x+1)^2& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}9x^2+6x+1\end{aligned} $$ | |
① | Find $ \left(3x+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}{ 3x } $ and $ B = \color{red}{ 1 }$. $$ \begin{aligned}\left(3x+1\right)^2 = \color{blue}{\left( 3x \right)^2} +2 \cdot 3x \cdot 1 + \color{red}{1^2} = 9x^2+6x+1\end{aligned} $$ |