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

Toán Lớp 8: 3x(x-7)+x-7=0 ai giúp mình được không ạ

Toán Lớp 8: 3x(x-7)+x-7=0 ai giúp mình được không ạ

Comments ( 2 )

  1. $\\$
    3x(x-7)+x-7=0
    <=> 3x(x-7)+(x-7)=0
    <=> (x-7)(3x+1)=0
    TH1 :
    x-7=0
    <=> x=7
    TH2 :
    3x+1=0
    <=>3x=-1
    <=> x=(-1)/3
    Vậy x=7,x=(-1)/3
     

  2. 3x(x – 7) + x – 7 = 0
    ⇔ 3x(x – 7) + (x – 7) = 0
    ⇔ (x – 7)(3x + 1) = 0
    ⇔ \(\left[ \begin{array}{l}x – 7 = 0\\3x + 1 = 0\end{array} \right.\) 
    ⇔ \(\left[ \begin{array}{l}x = 7\\x = -\frac{1}{3}\end{array} \right.\) 
    Vậy x ∈ {7; -$\frac{1}{3}$}
    $\textit{Shiii}$
     

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