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

Toán Lớp 8: Tìm x: x^2 – 4 =0 x^2 + 2x =0

Toán Lớp 8: Tìm x:
x^2 – 4 =0
x^2 + 2x =0

Comments ( 2 )

  1. x^2 – 4 =0
    (x+2)(x-2)=0
    =>\(\left[ \begin{array}{l}x+2=0\\x-2=0\end{array} \right.\) 
    =>\(\left[ \begin{array}{l}x=-2\\x=2\end{array} \right.\) 
    \text{Vậy} x ∈{-2;2}
    x^2 + 2x =0
    x(x+2)=0
    =>\(\left[ \begin{array}{l}x=0\\x+2=0\end{array} \right.\) 
    =>\(\left[ \begin{array}{l}x=0\\x=-2\end{array} \right.\) 
    \text{Vậy}   x  \in  {0;-2}

  2. Giải đáp+Lời giải và giải thích chi tiết:
     a) x^2-4=0
    <=>x^2-2^2=0
    <=>(x-2)(x+2)=0
    <=>$\left[\begin{matrix} x-2=0\\ x+2=0\end{matrix}\right.$
    <=>$\left[\begin{matrix} x=2\\ x=-2\end{matrix}\right.$
     Vậy x∈{-2; 2}
     b) x^2+2x=0
    <=>x(x+2)=0
    <=>$\left[\begin{matrix} x=0\\ x+2=0\end{matrix}\right.$
    <=>$\left[\begin{matrix} x=0\\ x=-2\end{matrix}\right.$
     Vậy x∈{0; -2}

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