Multiply $4$ by $ \dfrac{s}{s^2} $ to get $ \dfrac{ 4s }{ s^2 } $.

Step 1: Write $ 4 $ as a fraction by putting $ \color{red}{1} $ in the denominator.

Step 2: Multiply numerators and denominators.

Step 3: Simplify numerator and denominator.

$$ \begin{aligned} 4 \cdot \frac{s}{s^2} & \xlongequal{\text{Step 1}} \frac{4}{\color{red}{1}} \cdot \frac{s}{s^2} \xlongequal{\text{Step 2}} \frac{ 4 \cdot s }{ 1 \cdot s^2 } = \\[1ex] & \xlongequal{\text{Step 3}} \frac{ 4s }{ s^2 } \end{aligned} $$

Subtract $1$ from $ \dfrac{4s}{s^2} $ to get $ \dfrac{ \color{purple}{ -s^2+4s } }{ s^2 }$.

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 second fraction by $\color{blue}{s^2}$.

$$ \begin{aligned} \frac{4s}{s^2} -1 & \xlongequal{\text{Step 1}} \frac{4s}{s^2} - \frac{1}{\color{red}{1}} = \frac{ 4s }{ s^2 } - \frac{ 1 \cdot \color{blue}{ s^2 }}{ 1 \cdot \color{blue}{ s^2 }} = \\[1ex] & \xlongequal{\text{Step 2}} \frac{ \color{purple}{ 4s } }{ s^2 } - \frac{ \color{purple}{ s^2 } }{ s^2 }=\frac{ \color{purple}{ -s^2+4s } }{ s^2 } \end{aligned} $$