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

Toán Lớp 8: 1 ) 3x-3-7(x^2-1)=0 2) 2x+6+5(x^2+3x)=0 3) x^2-2X-9(-2X+4)=0 4) 3X^2-9X+8(-X+3)=0

Tháng Mười Hai 31, 2022 Toán học 2 Comments 0 views

Toán Lớp 8: 1 ) 3x-3-7(x^2-1)=0
2) 2x+6+5(x^2+3x)=0
3) x^2-2X-9(-2X+4)=0
4) 3X^2-9X+8(-X+3)=0

Comments ( 2 )

  1. tuyethutanhthu
    tuyethutanhthu
    31 Tháng Mười Hai, 2022 at 6:44 sáng
    Reply
    $1. 3x-3-7(x²-1)=0$
    $⇔3(x-1)-7(x-1)(x+1)=0$
    $⇔(x-1)(3-7x-7)=0$
    $⇔(x-1)(-7x-4)=0$
    $⇔x-1=0$
       $-7x-4=0$
    $⇔x=1$
     $ -7x=4$
    $⇔x=1$
      $  x=-4/7$
    $2. 2x+6+5(x²+3x)=0$
    $⇔2(x+3)+5x(x+3)=0$
    $⇔(5x+2)(x+3)=0$
    $⇔5x+2=0$
     $   x+3=0$
    $⇔5x=-2$
       $ x=-3$
    $⇔x=-2/5$
       $ x=-3$
    $3. x²-2x-9(-2x+4)=0$
    $⇔x(x-2)+18(x-2)=0$
    $⇔(x+18)(x-2)=0$
    $⇔x+18=0$
     $   x-2=0$
    $⇔x=-18$
       $ x=2$
    $4. 3x²-9x+8(-x+3)=0$
    $⇔3x(x-3)-8(x-3)=0$
    $⇔(3x-8)(x-3)=0$
    $⇔3x-8=0$
    $    x-3=0$
    $⇔3x=8$
      $  x=3$
    $⇔x=8/3$
       $ x=3$
        

  2. dananhnhu2k4
    dananhnhu2k4
    31 Tháng Mười Hai, 2022 at 6:43 sáng
    Reply
    Giải đáp:
     
    Lời giải và giải thích chi tiết:
    a) 3x-3-7(x^2-1)=0
    <=> 3(x-1)-7(x-1)(x+1)=0
    <=> 3(x-1)-(7x+7)(x-1)=0
    <=> (x-1)(3-7x-7)=0
    <=> (x-1)(-4-7x)=0
    <=> $\left[ \begin{array}{l}x-1=0\\-4-7x=0\end{array} \right.$
    <=> $\left[ \begin{array}{l}x=1\\x=-7/4\end{array} \right.$
    Vậy x=-7/4, 1
    b) 2x+6+5(x^2+3x)=0
    <=> 2(x+3)+5x(x+3)=0
    <=> (x+3)(2+5x)=0
    <=> $\left[ \begin{array}{l}x+3=0\\2+5x=0\end{array} \right.$
    <=> $\left[ \begin{array}{l}x=-3\\x=-2/5\end{array} \right.$
    Vậy x=-3, -2/5
    c) x^2-2x-9(-2x+4)=0
    <=> x(x-2)+18(x-2)=0
    <=> (x+18)(x-2)=0
    <=> $\left[ \begin{array}{l}x+18=0\\x-2=0\end{array} \right.$
    <=> $\left[ \begin{array}{l}x=-18\\x=2\end{array} \right.$
    Vậy x=-18, 2
    d) 3x^2-9x+8(-x+3)=0
    <=> 3x(x-3)-8(x-3)=0
    <=> (3x-8)(x-3)=0
    <=> $\left[ \begin{array}{l}x-3=0\\3x-8=0\end{array} \right.$
    <=> $\left[ \begin{array}{l}x=3\\x=8/3\end{array} \right.$
    Vậy x=3, 8/3

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

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