| $$ \begin{aligned}2 \cdot \frac{x}{1+x^2}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}\frac{2x}{x^2+1}\end{aligned} $$ | |
| ① | Multiply $2$ by $ \dfrac{x}{1+x^2} $ to get $ \dfrac{2x}{x^2+1} $. Step 1: Write $ 2 $ as a fraction by putting $ \color{red}{1} $ in the denominator. Step 2: Multiply numerators and denominators. Step 3: Simplify numerator and denominator. $$ \begin{aligned} 2 \cdot \frac{x}{1+x^2} & \xlongequal{\text{Step 1}} \frac{2}{\color{red}{1}} \cdot \frac{x}{1+x^2} \xlongequal{\text{Step 2}} \frac{ 2 \cdot x }{ 1 \cdot \left( 1+x^2 \right) } = \\[1ex] & \xlongequal{\text{Step 3}} \frac{ 2x }{ 1+x^2 } = \frac{2x}{x^2+1} \end{aligned} $$ |