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

Toán Lớp 6: Tìm x (X + 25) . (24-3x) = 0 (X-2).(x+7) bé hơn 0

Toán Lớp 6: Tìm x
(X + 25) . (24-3x) = 0
(X-2).(x+7) bé hơn 0

Comments ( 1 )

  1. Tìm x :
    (x+25)(24-3x)=0
    => \(\left[ \begin{array}{l}x+25=0\\24-3x=0\end{array} \right.\) 
    => \(\left[ \begin{array}{l}x=-25\\3x=24\end{array} \right.\) 
    => \(\left[ \begin{array}{l}x=-25\\x=8\end{array} \right.\) 
    Vậy x∈{-25;8}
    Giải thích :
    – ab=0=> \(\left[ \begin{array}{l}a=0\\b=0\end{array} \right.\) 
    (x-2)(x+7)<0
    => $\begin{cases}\left[ \begin{array}{l}x-2<0\\x+7>0\end{array} \right.\\ \left[ \begin{array}{l}x-2>0\\x+7<0\end{array} \right.\end{cases}$
    => $\begin{cases}\left[ \begin{array}{l}x<2\\x> -7\end{array} \right. \\ \left[ \begin{array}{l}x>2\\x< -7\end{array} \right. (KTM)\end{cases}$
    =>-7<x<2
    =>x∈{-6;-5;-4;3;-2;-1;0;1}
    Vậy x∈{-6;-5;-4;-3;-2;-1;0;1}
    Giải thích :
    * Nếu x-2>0;x+7>0=>(x-2)(x+7)>0(KTM)
    * Nếu x-2<0;x+7<0=>(x-2)(x+7)>0(KTM)
    * Nếu x-2<0;x+7>0=>(x-2)(x+7)<0(TM)
    * Nếu x-2>0;x+7<0=>(x-2)(x+7)<0(TM)
    => Để (x-2)(x+7)<0=>x-2<0;x+7>0 hoặc x-2>0;x+7<0

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

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