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

Toán Lớp 8: Tìm x 2 a) 2(x+5) – x -5x

Toán Lớp 8: Tìm x 2
a) 2(x+5) – x -5x

Comments ( 2 )

  1. Giải:
    2(x + 5) – x^2 – 5x = 0
    -> 2(x + 5) – x(x + 5) = 0
    -> (x + 5)(2 – x) = 0
    -> \(\left[ \begin{array}{l}x+5=0\\2-x=0\end{array} \right.\) 
    -> \(\left[ \begin{array}{l}x=-5\\x = 2\end{array} \right.\) 
    Vậy S = {-5; 2}

  2. Giải đáp:
     
    Lời giải và giải thích chi tiết:
    2(x+5)-x^2-5x=0
    ⇔ 2x + 10 – x^2 – 5x = 0
    ⇔ -x^2 – (5x-2x) + 10 = 0
    ⇔ -x^2 – 3x + 10 = 0
    ⇔ -(x^2+3x-10) = 0
    ⇔ -[(x^2-2x)+(5x-10)] = 0
    ⇔ -[x(x-2)+5(x-2)] = 0
    ⇔ -(x+5)(x-2) = 0
    ⇔\(\left[ \begin{array}{l}x+5=0\\x-2=0\end{array} \right.\) 
    ⇔\(\left[ \begin{array}{l}x=-5\\x=2\end{array} \right.\) 
    Vậy S = {-5,2}

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

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