\(a+\frac{-500\%\div\frac{1}{-2}}{3^3}=a^3\)
\(\Leftrightarrow a+\frac{-5\div\frac{-1}{2}}{3^3}=a^3\)
\(\Leftrightarrow a+\frac{10}{27}=a^3\)
\(\Rightarrow a+10:27=a^3\)
\(\Rightarrow10:27=a^3-a=a.\left(a^2-1\right)\)
\(\Rightarrow\)\(0,3703....=a.\left(a^2-1\right)\)
\(\Rightarrow a\in\varphi\) nếu a là số nguyên.