Question

$\frac{ x^{2} }{5} - \frac{x}{15} =0$

Answer 1

$\dfrac{x^{2}}{5}-\dfrac{x}{15} =0\Longrightarrow3x^2-x =0\Longrightarrow x(3-x)=0\Longrightarrow\begin{cases}x_1=0\\3-x_2=0\rightarrow x_2=3\end{cases}\\\\ S=\{0,3\}$