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

Toán Lớp 8: `a) x + 5x^2 =0` `b) 2(x + 5) – x^2 – 5x = 0`

Toán Lớp 8: a) x + 5x^2 =0
b) 2(x + 5) – x^2 – 5x = 0

Comments ( 2 )

  1. Giải đáp:
     a) $\left[ \begin{array}{l}x=0\\x=-1/5\end{array} \right.$
    b) $\left[ \begin{array}{l}x=2\\x=-5\end{array} \right.$
    Lời giải và giải thích chi tiết:
    a) x+5x^2=0
    <=> x(1+5x)=0
    <=>  $\left[ \begin{array}{l}x=0\\1+5x=0\end{array} \right.$
    <=> $\left[ \begin{array}{l}x=0\\x=-1/5\end{array} \right.$
    Vậy x=0 hoặc x=-1/5
    b) 2(x+5)-x^2-5x=0
    <=> 2(x+5)-x(x+5)=0
    <=> (2-x)(x+5)=0
    <=> $\left[ \begin{array}{l}2-x=0\\x+5=0\end{array} \right.$
    <=> $\left[ \begin{array}{l}x=2\\x=-5\end{array} \right.$
    Vậy x=2 hoặc x=-5

  2. a) x + 5x² = 0
    ⇔ x(1+5x)=0
    ⇔ x = 0 hoặc 1+5x = 0
    ⇔ x = 0 hoặc 5x = -1
    ⇔ x = 0 hoặc x = -1/5
    b) 2(x+5) – x² – 5x = 0
    ⇔ 2(x+5) – x(x-5) = 0
    ⇔ x+5 = 0 hoặc 2-x=0
    ⇔ x = – 5 hoăc x = 2
     

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