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

Toán Lớp 7: Tìm x : a,4 ( 3x-1 ) -2 (5-3x) = -12 b,2x (x-1) -3 ( x^2 -4x + x +(x+2) = -3

Toán Lớp 7: Tìm x :
a,4 ( 3x-1 ) -2 (5-3x) = -12
b,2x (x-1) -3 ( x^2 -4x + x +(x+2) = -3

Comments ( 2 )

  1. a)4(3x-1)-2(5-3x)=-12
    ⇔12x-4-10+6x=-12
    ⇔18x=2
    ⇔x=1/9
    Vậy S=1/9
    b)2x(x-1)-3(x²-4x)+x+(x+2)=-3
    ⇔2x²-2x-3x²-12x-3x-3x-6=-3
    ⇔-x²+4x-3=0
    ⇔(x-3)(x-1)=0
    ⇔x=3 hoặcx=1
    Vậy S={3;1}

  2. Giải đáp : 
    a) x = \frac{1}{9}
    b) S ={3;1}
    Lời giải và giải thích chi tiết :
    a) 4 ( 3x-1 ) -2 (5-3x) = -12
    => 12x -4 -10+6x =-12
    => 12x+6x=-12+4+10
    => 18x = 2
    => \frac{1}{9}
    Vậy S={\frac{1}{9 }}
    b) 2x (x-1) -3 ( x^2 -4x + x + x+2) = -3
    => 2x^2 -2x-3x^2 +12x -3x -3x -6 = -3
    => -x^2 +4x -6=-3
    => -x^2+4x-3=0
    => x^2 -4x +3
    => (x-3)(x-1) =0
    => \(\left[ \begin{array}{l}x-3=0\\x-1=0\end{array} \right.\)
    =>\(\left[ \begin{array}{l}x=3\\x=1\end{array} \right.\)  
    Vậy S={3;1}
     

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