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

Toán Lớp 8: Bài 2. Tìm x c. (x-1)(x+2)=x+2

Toán Lớp 8: Bài 2. Tìm x
c. (x-1)(x+2)=x+2

Comments ( 2 )

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

  2. (x-1)(x+2)=x+2
    ⇔ x² + 2x – x – 2 – x – 2 = 0
    ⇔ x² – 4 = 0
    ⇔ (x-2)(x+2)=0
    ⇔ x = 2 hoặc x = -2
     

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

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