$$ \left( \color{blue}{1-itw}\right) \cdot 2mw = 2mw-2imtw^2 $$

Multiply $qrst$ by $ \dfrac{s}{2mw-2imtw^2} $ to get $ \dfrac{qrs^2t}{-2imtw^2+2mw} $.

Step 1: Write $ qrst $ as a fraction by putting $ \color{red}{1} $ in the denominator.

Step 2: Multiply numerators and denominators.

Step 3: Simplify numerator and denominator.

$$ \begin{aligned} qrst \cdot \frac{s}{2mw-2imtw^2} & \xlongequal{\text{Step 1}} \frac{qrst}{\color{red}{1}} \cdot \frac{s}{2mw-2imtw^2} \xlongequal{\text{Step 2}} \frac{ qrst \cdot s }{ 1 \cdot \left( 2mw-2imtw^2 \right) } = \\[1ex] & \xlongequal{\text{Step 3}} \frac{ qrs^2t }{ 2mw-2imtw^2 } = \frac{qrs^2t}{-2imtw^2+2mw} \end{aligned} $$

Multiply $ \dfrac{qrs^2t}{-2imtw^2+2mw} $ by $ 1+i $ to get $ \dfrac{iqrs^2t+qrs^2t}{-2imtw^2+2mw} $.

Step 1: Write $ 1+i $ as a fraction by putting $ \color{red}{ 1 } $ in the denominator.

Step 2: Multiply numerators and denominators.

Step 3: Simplify numerator and denominator.

$$ \begin{aligned} \frac{qrs^2t}{-2imtw^2+2mw} \cdot 1+i & \xlongequal{\text{Step 1}} \frac{qrs^2t}{-2imtw^2+2mw} \cdot \frac{1+i}{\color{red}{1}} = \\[1ex] & \xlongequal{\text{Step 2}} \frac{ qrs^2t \cdot \left( 1+i \right) }{ \left( -2imtw^2+2mw \right) \cdot 1 } \xlongequal{\text{Step 3}} \frac{ qrs^2t+iqrs^2t }{ -2imtw^2+2mw } = \\[1ex] &= \frac{iqrs^2t+qrs^2t}{-2imtw^2+2mw} \end{aligned} $$