| $$ \begin{aligned}(\frac{x}{y}+4)^2(\frac{x}{y}+1)-\frac{1}{x^3}-c& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}(\frac{x}{y}+4)^2\frac{x+y}{y}-\frac{1}{x^3}-c\end{aligned} $$ | |
| ① | Add $ \dfrac{x}{y} $ and $ 1 $ to get $ \dfrac{ \color{purple}{ x+y } }{ y }$. Step 1: Write $ 1 $ as a fraction by putting $ \color{red}{ 1 } $ in the denominator. Step 2: To add raitonal expressions, both fractions must have the same denominator. |