$$ \begin{aligned}sqrt(x^2+100^2)& \xlongequal{ }sqrt(x^2+10000) \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}qrstx^2+10000qrst\end{aligned} $$ | |
① | Multiply $ \color{blue}{qrst} $ by $ \left( x^2+10000\right) $ $$ \color{blue}{qrst} \cdot \left( x^2+10000\right) = qrstx^2+10000qrst $$ |