Tìm $x:$ $a,$ $4x$ $(x-2)$ $-5$ $(3-x)$ $-4x^{2}$=6 $b,$ $(x-3)^{2}$ $=$ $(2x-1)^{2}$ $c,$ $(x-3)$ $(x^{2}+3x+9)$ $-x$ $(x-2)

2 bình luận về “Tìm $x:$ $a,$ $4x$ $(x-2)$ $-5$ $(3-x)$ $-4x^{2}$=6 $b,$ $(x-3)^{2}$ $=$ $(2x-1)^{2}$ $c,$ $(x-3)$ $(x^{2}+3x+9)$ $-x$ $(x-2)”

1. $a,$ $4x(x-2)$ $-5(3-x)$ $-4x^{2}$ $=6$

     $4x^{2}$ $-8x$ $-15$ $+5x$ $-4x^{2}$ $=6$

     $-3x$ $-15$ $=6$

     $-3x$ $=21$

     $x=-7$

   $b,$ $(x-3)^{2}$ $=(2x-1)^{2}$

     $x^{2} -6x+9=4x^{2}-4x+1$ 

     $-3x^{2}-2x+8=0$ 

     $-3x^{2}-6x+4x+8=0$ 

     $-[3x(x+2)] +4(x+2)=0$

     $(x+2)(-3x+4)=0$

   $=>$\(\left[ \begin{array}{l}x=-2\\x=\frac{4}{3}\end{array}\right.\)

   $c,$ $(x-3)(x^{2}+3x+9)-x(x-2)(x+2)+2x=0$

     $x^{3} -27 -(x^{2}-2x)(x+2)+2x=0$

     $x^{3}-27-x^{3}-2x^{2}+2x^{2}+4x+2x=0$

     $6x-27=0$

     $x=$$\frac{27}{6}$ 

    

   Trả lời
2. $\text{4x (x – 2) – 5( 3 – x) – 4x^2 = 6}$

   $\text{4x^2 – 8x – 15 + 5x – 4x^2 = 6}$

   $\text{(4x^2 – 4x^2)+(-8x + 5x) = 6 + 15}$

   $\text{-3x = 21}$

   $\text{x = $\dfrac{21}{-3}$}$

   $\text{x = -7}$

   $\text{(x – 3)^2 = (2x – 1)^2}$

   $\text{x^2 – 6x + 9 = 4x^2 – 4x + 1}$

   $\text{x^2 – 4x^2 – 6x + 4x + 9 – 1 = 0}$

   $\text{-3x^2 -2x + 8 = 0}$

   $\text{-3x^2 – 6x + 4x + 8 = 0}$

   $\text{-3x (x+2) + 4(x+2) = 0}$

   $\text{(x+2)(-3x + 4) = 0}$

   $\text{$\left[\begin{matrix} x + 2 = 0\\ -3x + 4 = 0\end{matrix}\right.$}$

   $\text{$\left[\begin{matrix} x = -2\\ -3x = -4\end{matrix}\right.$}$

   $\text{$\left[\begin{matrix} x = -2\\ x = \dfrac{4}{3}\end{matrix}\right.$}$

   $\text{(x – 3) (x^2 + 3x + 9) – x (x – 2)(x + 2)+ 2x = 0}$

   $\text{x^3 + 3x^2 + 9x -3x^2 – 9x – 27 – x (x^2 – 4) + 2x = 0}$

   $\text{x^3 – 27 – x^3 + 4x + 2x = 0}$

   $\text{6x = 27}$

   $\text{x = $\dfrac{27}{6}$}$

   Trả lời