-x^2+5x-6=0; (x-1)(x^2+5x-2)-(x^3-1)=0 ;2x^2+5x+3=0

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1. a)-x^2+5x-6=0

   <=>-x2+2x+3x-6=0

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

   <=>(x-2)(-x+3)=0<=>x=2  , x=3

   vậy tập nghiệm của pt đã cho là s={2,3}

   b)(????−1)(????2+5????−2)−(????3−1)=0

   <=>????(????2+5????−2)−(????2+5????−2)−(????3−1)=0

   <=>????3+5????2−2????−(????2+5????−2)−(????3−1)=0

   <=>????3+4????2−2????−5????+2−1(????3−1)=0

   <=>????3+4????2−7????+2−1(????3−1)=0

   <=>4????2−7????+3=0<=>4×2-4x-3x+3=0

   <=>4x(x-1)-3(x-1)=0<=>(x-1)(4x-3)=0<=>????=1 , ????=3/4

   vậy ….

   c)2x^2+5x+3=0

   <=>2×2+2x+3x+3=0<=>2x(x+1)+3(x+1)=0

   vậy …..

   <=>(x+1)(2x+3)=0<=>????=−1   ,   ????=−3/2

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2. -x^2+5x-6=0

   -(x^2-5x+6)=0

   -(x-3)(x-2) = 0

   ⇒ x-3=0 hoặc x-2=0

         x-3=0 ⇔ x=3

         x-2=0 ⇔ x=2

    vậy S={3  ;2}

   (x-1)(x^2+5x-2)-(x^3-1)=0 

   (x-1)(x^2+5x-2)-(x-1)(x^2+x+1)=0

   (x-1)(x^2+5x-2-x^2-x-1)=0

   (x-1)(4x-3)=0

   ⇒ x-1=0 hoặc 4x-3=0

       x-1=0 ⇔ x=1

      4x-3=0 ⇔ x=3/4

    vậy S={1 ; 3/4}

   2x^2+5x+3=0

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

   ⇒ 2x-1=0 hoặc x+3=0

       2x-1=0 ⇔ x=1/2

       x+3=0 ⇔ x=-3

    vậy S={1/2 ; -3}

    

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