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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 8: Tìm x, bik 2x(x-5) -x(3x+2) =x(3-3x)

Toán Lớp 8: Tìm x, bik
2x(x-5) -x(3x+2) =x(3-3x)

Comments ( 2 )

  1. 2x(x-5)-x(3x+2)=x(3-3x)
    <=>2x^2-10x-3x^2-2x=3x-3x^2
    <=>-x^2+3x^2-10x-2x-3x=0
    <=>2x^2-15x=0
    <=>x(2x-15)=0
    <=>\(\left[ \begin{array}{l}x=0\\2x-15=0\end{array} \right.\) 
    <=>\(\left[ \begin{array}{l}x=0\\x=\dfrac{15}{2}\end{array} \right.\) 
    Vậy x=0 hoặc x=(15)/2

  2. $\text{2x( x – 5 ) – x( 3x + 2 ) = x( 3 – 3x )}$
    $\text{⇔ 2$x^{2}$ – 10x – 3$x^{2}$ – 2x = 3x – 3$x^{2}$ }$
    $\text{⇔ 2$x^{2}$ – 10x – 2x = 3x}$
    $\text{⇔ 2$x^{2}$ – 12x = x}$
    $\text{⇔ 2$x^{2}$ – 12x – 3x = 0}$
    $\text{⇔ 2$x^{2}$ – 15x = 0}$
    $\text{⇔ x( 2x – 15 ) = 0}$
    $\text{⇔}$ $\left[\begin{matrix} x = 0\\ 2x – 15 = 0\end{matrix}\right.$
    $\text{⇔}$ $\left[\begin{matrix} x = 0\\ x = \dfrac{15}{2}\end{matrix}\right.$
    Vậy $\text{x ∈ { 0; $\dfrac{15}{2}$ } }$

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222-9+11+12:2*14+14 = ? ( )