`a, (x+3)(x-2)-4(x+3/4)+3x=0`
`<=>x^2-2x+3x-6-4x-3+3x=0`
`<=>x^2-9=0`
`<=>(x-3)(x+3)=0`
`<=>`\(\left[ \begin{array}{l}x-3=0\\x+3=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=3\\x=-3\end{array} \right.\)
Vậy `S = {-3,3}`
`b,(x^2+5)(x+2)+x(5-2x)=17`
`<=>x^3+2x^2-5x-10+5x-2x^2=17`
`<=>x^3+2x^2-2x^2-5x+5x-10+-17=0`
`<=>x^3-27=0`
`<=>x^3=3^3`
`<=>x=3`
Vậy `S={3}`
`c,2x^2+3(x-1)(x+1)=5x(x+1)`
`<=>2x^2+3(x^2-1)=5x(x+1)`
`<=>2x^2-3+3x^2+3=5x^2+5x`
`<=>2x^2+3x^2-5x^2-5x=-3`
`<=>-5x=-3` `<=>x=5/3`
Vậy `S = {5/3}`
