Subtract $ \dfrac{x^2}{9} $ from $ 1 $ to get $ \dfrac{ \color{purple}{ -x^2+9 } }{ 9 }$.

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

Step 2: To subtract raitonal expressions, both fractions must have the same denominator.
We can create a common denominator by multiplying the first fraction by $\color{blue}{ 9 }$.

$$ \begin{aligned} 1- \frac{x^2}{9} & \xlongequal{\text{Step 1}} \frac{1}{\color{red}{1}} - \frac{x^2}{9} = \frac{ 1 \cdot \color{blue}{ 9 }}{ 1 \cdot \color{blue}{ 9 }} - \frac{ x^2 }{ 9 } = \\[1ex] & \xlongequal{\text{Step 2}} \frac{ \color{purple}{ 9 } }{ 9 } - \frac{ \color{purple}{ x^2 } }{ 9 }=\frac{ \color{purple}{ -x^2+9 } }{ 9 } \end{aligned} $$

Multiply $qrst$ by $ \dfrac{-x^2+9}{9} $ to get $ \dfrac{ -qrstx^2+9qrst }{ 9 } $.

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.

$$ \begin{aligned} qrst \cdot \frac{-x^2+9}{9} & \xlongequal{\text{Step 1}} \frac{qrst}{\color{red}{1}} \cdot \frac{-x^2+9}{9} \xlongequal{\text{Step 2}} \frac{ qrst \cdot \left( -x^2+9 \right) }{ 1 \cdot 9 } = \\[1ex] & \xlongequal{\text{Step 3}} \frac{ -qrstx^2+9qrst }{ 9 } \end{aligned} $$