(x+1)mũ3 -(x-1) (x mũ 2+x+1)-3x=5

2 bình luận về “(x+1)mũ3 -(x-1) (x mũ 2+x+1)-3x=5”

1. (x + 1)^3 – (x – 1)(x^2 + x + 1) – 3x = 5

   => x^3 + 3x^2 + 3x + 1 – x^3 – x^2 – x + x^2 + x + 1 – 3x = 5

   => 3x^2 = 5 -1 -1

   => 3x^2 = 3

   => x^2 = 1

   => x^2 = (+-1)^2

   => x = +-1

   vậy x = +-1

   $#duong612009$

   Trả lời
2. Lời giải:
   

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

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

   =>x^3+3x^2+3x+1-x^3+1-3x-5=0

   =>3x^2-3=0

   =>3x^2=3

   =>x^2=1

   =>x=\pm1

   Vậy x\in{1;-1}

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