`a)(x+1)(2x-4)=0`
`<=>` \(\left[ \begin{array}{l}x+1=0\\2x-4=0\end{array} \right.\) `<=>` \(\left[ \begin{array}{l}x=-1\\x=2\end{array} \right.\)
Vậy `S={-1;2}`
`b)2x(x-3)+5(x-3)=0`
`<=>(2x+5)(x-3)=0`
`<=>` \(\left[ \begin{array}{l}2x+5=0\\x-3=0\end{array} \right.\) `<=>` \(\left[ \begin{array}{l}x=-\dfrac{5}{2}\\x=3\end{array} \right.\)
Vậy `S={-5/2;3}`
`c)(x-3)(3x+2)=(x-3)(x+5)`
`<=>(x-3)(3x+2)-(x-3)(x+5)=0`
`<=>(x-3)(3x+2-x-5)=0`
`<=>(x-3)(2x-3)=0`
`<=>` \(\left[ \begin{array}{l}x-3=0\\2x-3=0\end{array} \right.\) `<=>` \(\left[ \begin{array}{l}x=3\\x=\dfrac{3}{2}\end{array} \right.\)
Vậy `S={2;3/2}`
