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

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1. Đáp án:

    `a)x=7/5`

    `b)“S={0;-3}`

   Giải thích các bước giải:

   `a)(x-1)^2-(x-1)(x+1)=3x-5`

   `⇔(x-1)(x-1-x-1)=3x-5`

   `⇔(x-1).(-2)=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`$\neq$`-11`;`x`$\neq$`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^2-9x+33=-12x+33`

   `⇔x^2+3x=0`

   `⇔x(x+3)=0`

   `1)x=0(tm)`

   `2)x+3=0⇔x=-3(tm)`

   `Vậy` `S={0;-3}`

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2. -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}`

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