a) 3x² - 5x = 0
⇔ x ( 3x - 5 ) = 0
⇔ \(\left[ \begin{array}{l}x=0\\3x-5 = 0\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}x=0\\x= 5 / 3\end{array} \right.\)
Vậy : pt có 2 nghiệm : x = 0 ; x = 5 / 3
b) 2x² - 3x - 2 = 0
⇔ 2x² - 4x + x - 2 = 0
⇔ 2x( x - 2 ) + ( x - 2 ) = 0
⇔ ( x - 2 )( 2x + 1 ) = 0
⇔ \(\left[ \begin{array}{l}x - 2 = 0\\2x + 1 = 0\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}x = 2\\x = -1 / 2\end{array} \right.\)
Vậy : pt có 2 nghiệm : x = 2 ; x = -1 / 2
