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

Toán Lớp 8: Tìm x: a) 5×2(2x-3) (2×2 3x 3)(3-2x)=6×3-9×2

Tháng Một 18, 2023 Toán học 1 Comment 0 views

Toán Lớp 8: Tìm x:
a) 5×2(2x-3) (2×2 3x 3)(3-2x)=6×3-9×2

Comments ( 1 )

  1. buianhtuan
    buianhtuan
    18 Tháng Một, 2023 at 4:55 sáng
    Reply
    a) 5x^2(2x-3)+(2x^2+3x+3)(3-2x)=6x^3-9x^2
    <=>10x^3-15x^2+(6x^2-4x^3+9x-6x^2+9-6x)-6x^3+9x^2=0
    <=> 4x^3-6x^2+(-4x^3+3x+9)=0
    <=> 4x^3-6x^2-4x^3+3x+9=0
    <=> -6x^2+3x+9=0
    <=> 2x^2-x-3=0
    <=> 2x^2-3x+2x-3=0
    <=> x(2x-3)+(2x-3)=0
    <=> (2x-3)(x+1)=0
    <=>\(\left[ \begin{array}{l}x=\dfrac{3}{2}\\x=-1\end{array} \right.\) 
    Vậy S={3/2;-1}
    b) (4x^2+2x)(x^2-x)+(4x^2+6)(x-x^2)=0
    <=> 4x^4-4x^3+2x^3-2x^2+4x^3-4x^4+6x-6x^2=0
    <=> 2x^3-8x^2+6x=0
    <=> 2x(x^2-4x+3)=0
    <=> 2x(x^2-x-3x+3)=0
    <=>2x[x(x-1)-3(x-1)]=0
    <=> 2x(x-1)(x-3)=0
    <=>\(\left[ \begin{array}{l}x=0\\x=1\\x=3\end{array} \right.\) 
    Vậy S={0;1;3}

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

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