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

Toán Lớp 8: x ² + 4x – 96 = 0 ==-..

Toán Lớp 8: x ² + 4x – 96 = 0
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Comments ( 2 )

  1. x^2 +4x – 96 =0
    -> x^2 + 2 . x . 2 + 4 – 100 =0
    -> (x+ 2)^2 – 100 =0
    -> (x+2)^2 =100
    -> x +2 = 10 hoặc x +2=  -10
    -> x = 8 hoặc x = -12
    Vậy x \in {8 ; -12} 

  2. $x^2+4x-96=0\\↔x^2+12x-8x-96=0\\↔(x^2+12x)-(8x+96)=0\\↔x(x+12)-8(x+12)=0\\↔(x-8)(x+12)=0\\↔\left[\begin{array}{1}x-8=0\\x+12=0\end{array}\right.\\↔\left[\begin{array}{1}x=8\\x=-12\end{array}\right.$
    Vậy $S=\{8;-12\}$

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

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