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 `a)` `x(2x-7)-4x+14=0`

`<=>x(2x-7)-2(2x-7)=0`

`<=>(2x-7)(x-2)=0`

`<=>`$\left[\begin{matrix} 2x-7=0\\ x-2=0\end{matrix}\right.$

`<=>`$\left[\begin{matrix} x=\dfrac{7}{2}\\ x=2\end{matrix}\right.$

`text{Vậy}` `S={7/2;2}`

 `b)` `x(x-1)+2x-2=0`

`<=>x(x-1)+2(x-1)=0`

`<=>(x-1)(x+2)=0`

`<=>`$\left[\begin{matrix} x-1=0\\ x+2=0\end{matrix}\right.$

`<=>`$\left[\begin{matrix} x=1\\ x=-2\end{matrix}\right.$

`text{Vậy}` `S={1;-2}`

 `c)` `x+x^2-x^3-x^4=0`

`<=>x^4+x^3-x^2-x=0`

`<=>x(x^3+x^2-x-1)=0`

`<=>x[x^2(x+1)-(x+1)]=0`

`<=>x(x+1)(x^2-1)=0`

`<=>x(x+1)(x-1)(x+1)=0`

`<=>`$\left[\begin{matrix} x=0\\ x+1=0\\ x-1=0\end{matrix}\right.$

`<=>`$\left[\begin{matrix} x=0\\ x=-1\\ x=1\end{matrix}\right.$

`text{Vậy}` `S={0;-1;1}`

 `d)` `2x^3+3x^2+2x+3=0`

`<=>x^2(2x+3)+(2x+3)=0`

`<=>(2x+3)(x^2+1)=0`

`text{vì}` `x^2geq0`

        `<=>x^2+1>0`

        `<=>x^2+1ne0`

`text{mà}` `(2x+3)(x^2+1)=0`

`=>2x+3=0`

`<=>x=-3/2`

`text{Vậy}` `S={-3/2}`