Đáp án:
Bài 1 :
`3x²+x=0`
`⇒x(3x+1)=0`
⇒\(\left[ \begin{array}{l}x=0\\3x+1=0\end{array} \right.\)
⇒\(\left[ \begin{array}{l}x=0\\3x=-1\end{array} \right.\)
⇒\(\left[ \begin{array}{l}x=0\\x=-1/3\end{array} \right.\)
`5x-x²=0`
`⇒x(x+5)=0`
⇒\(\left[ \begin{array}{l}x=0\\x+5=2\end{array} \right.\)
⇒\(\left[ \begin{array}{l}x=0\\x=5\end{array} \right.\)
Bài 2 :
`x²-6=3`
`⇒x²=9`
`⇒x²=3²`
`⇒x=±3`
