$\text{Để đa thức có nghiệm}$
$\text{⇔ (x - 2,5)(3x + 1,5) = 0}$
$\text{⇔ \(\left[ \begin{array}{l}x - 2,5 = 0\\3x + 1,5 = 0\end{array} \right.\) }$
$\text{⇔ \(\left[ \begin{array}{l}x = 2,5\\3x = -1,5\end{array} \right.\) }$
$\text{⇔ \(\left[ \begin{array}{l}x = 2,5\\x = -0,5\end{array} \right.\) }$