`a)`
`2x^2-3x+2x-3-x^2=x^2-4x+4`
`<=>2x^2-x^2-x^2-3x+2x+4x=3+4`
`<=>3x=7`
`<=>x=7:3` `
`<=>x=7/3`
Vậy `S={7/3}`
`b)`
`2x-4=6`
`<=>2x=10`
`<=>x=10:2`
`<=>x=5`
Vậy `S={5}`
`c)`
`3x+4=19`
`<=>3x=15`
`<=>x=15:3`
`<=>x=5`
Vậy `S={5}`
`d)`
`2(x+1)=3+2x`
`<=>2x+2=3+2x`
`<=>2x-2x=-2+3`
`<=>0x=1`
Vậy `S =∅`