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

Toán Lớp 8: Tìm x biết 6x^2 – 12x = 0 (x+1) = (x+1)^3 Giải giúp mình vs

Toán Lớp 8: Tìm x biết
6x^2 – 12x = 0
(x+1) = (x+1)^3
Giải giúp mình vs

Comments ( 2 )

  1. a) 6x² – 12x = 0
    ⇔ 6x(x – 2) = 0
    ⇔ \(\left[ \begin{array}{l}6x = 0\\x – 2 = 0\end{array} \right.\) 
    ⇔ \(\left[ \begin{array}{l}x = 0\\x = 2\end{array} \right.\) 
    Vậy x ∈ {0; 2}
    b) (x + 1) = (x + 1)³
    ⇔ (x + 1) – (x + 1)³ = 0
    ⇔ (x + 1)[1 – (x + 1)²] = 0
    ⇔ (x + 1)(1 – x² – 2x – 1) = 0
    ⇔ (x + 1)(-x² – 2x) = 0
    ⇔ (x + 1).(-x).(x + 2) = 0
    TH1: x + 1 = 0
    ⇔ x = -1
    TH2: -x = 0
    ⇔ x = 0
    TH3: x + 2 = 0
    ⇔ x = -2
    Vậy x ∈ {-2; -1; 0}
    c) 3x(x – 2020) – x +2020 = 0
    ⇔ 3x(x – 2020) – (x – 2020) = 0
    ⇔ (x – 2020)(3x – 1) = 0
    ⇔ \(\left[ \begin{array}{l}x – 2020 = 0\\3x – 1 = 0\end{array} \right.\) 
    ⇔ \(\left[ \begin{array}{l}x = 2020\\x = \frac{1}{3}\end{array} \right.\) 
    Vậy x ∈ {2020; $\frac{1}{3}$}
     

  2. Đáp án:
     
    Giải thích các bước giải:
     

    toan-lop-8-tim-biet-6-2-12-0-1-1-3-giai-giup-minh-vs

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