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

Toán Lớp 8: Tìm x biết $g)$ $x^{2}-6x=0$ $h)$ $2x^{3}$ $+5x^{2}-12x=0$

Tháng Bảy 6, 2022 Toán học 2 Comments 0 views

Toán Lớp 8: Tìm x biết
$g)$ $x^{2}-6x=0$
$h)$ $2x^{3}$ $+5x^{2}-12x=0$

Comments ( 2 )

  1. bichhhathu
    bichhhathu
    6 Tháng Bảy, 2022 at 2:41 chiều
    Reply
    Giải đáp:
    g)x^2-6x=0
    =>x.(x-6)=0
    => $\left[\begin{matrix} x=0\\ x-6=0\end{matrix}\right.$
    <=> $\left[\begin{matrix} x=0\\ x=6\end{matrix}\right.$
    h)2x^3+5x^2-12x=0
    =>x.(2x^2+5x-12)=0
    =>x.(2x^2+8x-3x-12)=0
    =>x.[2x.(x+4)-3(x+4)]=0
    =>x.(x+4).(2x-3)=0
    => $\left[\begin{matrix} x=0\\ x+4=0 \\ 2x-3=0\end{matrix}\right.$
    <=> $\left[\begin{matrix} x=0\\ x=-4 \\x=\dfrac{3}{2} \end{matrix}\right.$
     

  2. lanhuongthu
    lanhuongthu
    6 Tháng Bảy, 2022 at 2:40 chiều
    Reply
    g, x^2 – 6x = 0
    => x(x-6) = 0 
    => $\left[\begin{matrix} x = 0\\ x – 6 = 0\end{matrix}\right.$
    => $\left[\begin{matrix} x = 0\\ x = 6\end{matrix}\right.$
    Vậy x∈ {0; 6}                  
    h, 2x^3 + 5x^2 – 12x = 0
    => 2x^3 + 8x^2 – 3x^2 -12x = 0
    => 2x^2 . (x – 3/2) + 8x . (x – 3/2) = 0
    => (x – 3/2) (2x^2 +8x) = 0
    => (x – 3/2) x (2x + 8) = 0
    => $\left[\begin{matrix} x – \dfrac{2}{3} = 0\\ x = 0\\2x + 8 = 0\end{matrix}\right.$
    => $\left[\begin{matrix} x = \dfrac{2}{3}\\ x = 0\\x = -4\end{matrix}\right.$
    Vậy x∈ {2/3; 0; -4}

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

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