\[5x^{2} - 15x = 0\]
\[5x(x - 3) = 0\]
\[1)\ 5x = 0\]
\[x = 0.\]
\[2)\ x - 3 = 0\]
\[x = 3.\]
\[Ответ:x = 0;x = 3.\]