| $$ \begin{aligned}\frac{z^2+8z+16}{z^3-3z^2-28z}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}\frac{z+4}{z^2-7z}\end{aligned} $$ | |
| ① | Simplify $ \dfrac{z^2+8z+16}{z^3-3z^2-28z} $ to $ \dfrac{z+4}{z^2-7z} $. Factor both the denominator and the numerator, then cancel the common factor. $\color{blue}{z+4}$. $$ \begin{aligned} \frac{z^2+8z+16}{z^3-3z^2-28z} & =\frac{ \left( z+4 \right) \cdot \color{blue}{ \left( z+4 \right) }}{ \left( z^2-7z \right) \cdot \color{blue}{ \left( z+4 \right) }} = \\[1ex] &= \frac{z+4}{z^2-7z} \end{aligned} $$ |