Tap the blue circles to see an explanation.
$$ \begin{aligned}(x+y+a)^2& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}a^2+2ax+2ay+x^2+2xy+y^2\end{aligned} $$ | |
① | Multiply each term of $ \left( \color{blue}{x+y+a}\right) $ by each term in $ \left( x+y+a\right) $. $$ \left( \color{blue}{x+y+a}\right) \cdot \left( x+y+a\right) = x^2+xy+ax+xy+y^2+ay+ax+ay+a^2 $$ |
② | Combine like terms: $$ x^2+ \color{blue}{xy} + \color{red}{ax} + \color{blue}{xy} +y^2+ \color{green}{ay} + \color{red}{ax} + \color{green}{ay} +a^2 = \\ = a^2+ \color{red}{2ax} + \color{green}{2ay} +x^2+ \color{blue}{2xy} +y^2 $$ |