a) x ³+1+(x ²+x+1)=0 b) (3x+1) ² – x ² +`8x -16 =0 c) (x+1)(x-1) ²-(x+1)(x-2) ²

0 bình luận về “a) x ³+1+(x ²+x+1)=0 b) (3x+1) ² – x ² +`8x -16 =0 c) (x+1)(x-1) ²-(x+1)(x-2) ²”

1. a) $x^3+1+(x^2+x+1) = 0 $

   $\to (x^2+x+1).(x+1+1) = 0 $

   $\to (x^2+x+1).(x+2) = 0 $

   $\to x+2=0$ ( Do $x^2+x+1>0$ ) 

   $\to x=-2$

   b) $(3x+1)^2-x^2+8x-16=0$

   $\to (3x+1)^2-(x-4)^2 = 0 $

   $\to (3x+1-x+4).(3x+1+x-4) = 0 $

   $\to (2x+5).(4x-3) = 0 $

   $\to x = \dfrac{-5}{2}$ hoặc $x=\dfrac{3}{4}$

   c) $(x+1).(x-1)^2 – (x+1).(x-2)^2$

   $ = (x+1).[(x-1)^2-(x-2)^2]$

   $ = (x+1).(x-1-x+2).(x-1+x-2)$

   $ = (x+1).(2x-3)$

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