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

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

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

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

`<=> x-1=0` hoặc `2x-3=0`

`<=> x=1` hoặc `x=3/2`

Vậy `S={1;3/2}`

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

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

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

`<=>x+3=0` hoặc `-x+1=0`

`<=>x=-3` hoặc `x=1`

Vậy `S={-3;1}`

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

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

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

`<=>2x+1=0` hoặc `x-3=0`

`<=>x=-1/2` hoặc `x=3`

Vậy `S={-1/2;3}`

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

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

`<=> 2*2x=0`

`<=> 4x=0`

`<=>x=0`

Vậy `S={0}`

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

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

`<=> (x-2)(5x+4)=0`

`<=>x-2=0` hoặc `5x+4=0`

`<=>x=2` hoặc `x=-4/5`

Vậy `S={2;-4/5}`

`(5x-4)^2 -(3x-2)^2=0`

`<=>(5x-4-3x+2)(5x-4+3x-2)=0`

`<=> (2x-2)(8x -6)=0`

`<=> 2x-2=0` hoặc `8x-6=0`

`<=> x= 1` hoặc `x=3/4`

Vậy `S={1;3/4}`