`(8x-3)(3x+2)-(4x+7)(x+4)=(2x+1)(5x-1)`
`<=>8x(3x+2)-3(3x+2)-[4x(x+4)+7(x+4)]=2x(5x-1)+1(5x-1)`
`<=>24x^2+16x-9x-6-(4x^2+16x+7x+28)=10x^2-2x+5x-1`
`<=>24x^2+7x-6-4x^2-16x-7x-28-10x^2-3x+1=0`
`<=>(24x^2-4x^2-10x^2)+(7x-16x-3x-7x)+(-6-28+1)=0`
`<=>10x^2-19x-33=0`
`<=>10x^2+11x-30x-33=0`
`<=>x(10x+11)-3(10x+11)=0`
`<=>(x-3)(10x+11)=0`
`<=>` \(\left[ \begin{array}{l}x-3=0\\10x+11=0\end{array} \right.\) `<=>`\(\left[ \begin{array}{l}x=3\\10x=-11\end{array} \right.\) `<=>`\(\left[ \begin{array}{l}x=3\\x=\dfrac{-11}{10}\end{array} \right.\)
vậy `S={3;-11/10}`
