a, (x-1)^2-(x-1)(x+1)=3x-5 b,x/x+11+3/x-12=-12x+33/(x+11)(x-11)

-Đáp án+Giải thích các bước giải:

 `a)  (x-1)^2-(x-1)(x+1)=3x-5`

`⇔ (x-1)(x-1-x-1)=3x-5`

`⇔  -2.(x-1) =3x-5`

`⇔  -2x+2=3x-5`

`⇔  -5x = -7`

`⇔  x = 7/5`

  Vậy`S={7/5}`

`b) x/(x+11)+3/(x-12)=(-12x+33)/((x+11)(x-12)) (ĐKXĐ:x\ne-11, x\ne 12)`

`⇔ (x(x-12))/((x+11)(x-12))+(3(x+11))/((x+11)(x-12))=(-12x+33)/((x+11)(x-12))`

`⇒ x^2 – 12x +3x+33= -12x+33`

`⇔  x^2 +3x=0`

`⇔  x(x+3)=0`

`⇔`\(\left[ \begin{matrix}x=0\\x+3=0\end{matrix} \right.\) 

`⇔`\(\left[ \begin{matrix}x=0(t/m)\\x=-3(t/m)\end{matrix} \right.\) 

  Vậy `S={0; -3}`