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

Toán Lớp 8: x^2-6x-7=0 TIM X LAM IK!!

Toán Lớp 8: x^2-6x-7=0 TIM X
LAM IK!!

Comments ( 2 )

  1. $x^{2}$ – 6x – 7 = 0
    <=> $x^{2}$ + x – 7x -7 = 0
    <=> x(x+1) – 7 ( x+ 1) =0
    <=> (x+1)(x-7) = 0
    <=>$\left \{ {{x+1=0} \atop {x-7=0}} \right.$ 
    <=> $\left \{ {{x=-1} \atop {x=7}} \right.$ 
    vậy S = { -1 ; 7 }
    xin câu trả lời hay nhất nha

  2. $\\$
    Giải đáp + giải thích các bước giải :
    $x^2-6x-7=0\\⇔x^2-7x+x-7=0\\⇔(x^2-7x)+(x-7)=0\\⇔x(x-7)+(x-7)=0\\⇔(x-7)(x+1)=0\\⇔\left[ \begin{array}{l}x-7=0\\x+1=0\end{array} \right.\\⇔\left[ \begin{array}{l}x=7\\x=-1\end{array} \right.$
    Vậy $x=7,x=-1$
     

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