$#Dino$
`x(x-2)-(x+2)(x-3)=7`
`⇔x²-2x-(x²-x-6)=7`
`⇔x²-x²+x-2x=7-6`
`⇔-x=1`
`⇔x=-1`
Vậy `S={-1}`
.................
`b) (x-3)/(x+1)=x²/(x²-1)`
`ĐKXĐ; x`$\neq$ `±1`
`⇔((x-3)(x-1))/(x²-1)=x²/(x²-1)`
`⇒(x-3)(x-1)=x²`
`⇔x²-4x+3=x²`
`⇔-4x=-3`
`⇔x=3/4`
Vậy `S={3/4}`
