`(x-2)(7-3x)=(x-2)(4x-3)`

`<=> (x-2)(7-3x)-(x-2)(4x-3)=0`

`<=> (x-2)(7-3x-4x+3)=0`

`<=> (x-2)(10-7x)=0`

`<=> [(x-2=0),(10-7x=0):} `

`<=>` $\left[\begin{matrix} x=2\\ x=\dfrac{10}{7}\end{matrix}\right.$

Vậy `S = { 2 ; 10/7 }`

`-----------`

`3x^2 - 3x = (x-1)(x+3)`

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

`<=> (x-1)(3x-x-3) = 0`

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

`<=> [(x-1=0),(2x-3=0):} `

`<=>` $\left[\begin{matrix} x=1\\ x=\dfrac{3}{2}\end{matrix}\right.$

Vậy `S={1;3/2}`