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

Toán Lớp 8: X mũ 3 +(x-1) mũ 3 = (2x-1) mũ 3

Tháng Mười Một 18, 2022 Toán học 2 Comments 0 views

Toán Lớp 8: X mũ 3 +(x-1) mũ 3 = (2x-1) mũ 3

Comments ( 2 )

  1. thaolanphuobg
    thaolanphuobg
    18 Tháng Mười Một, 2022 at 12:31 chiều
    Reply
    x^3+(x-1)^3=(2x-1)^3
    <=> x^3+x^3-3x^2+3x-1=8x^3-12x^2+6x-1
    <=> 2x^3-3x^2+3x-1-8x^3+12x^2+6x-1=0
    <=> (x^3+x^3-8x^3)+(12x^2-3x^2)+(3x-6x)-1+1=0
    <=> -6x^3+9x^2-3x=0
    <=> -3x(2x^2-3x+1)=0
    <=> -3x(2x^2-2x-x+1)=0
    <=> -3x[2x(x-1)-(x-1)]=0
    <=> -3x(2x-1)(x-1)=0
    <=> [(-3x=0),(2x-1=0),(x-1=0):} <=> \(\left[ \begin{array}{l}x=0\\x=\dfrac{1}{2}\\x=1\end{array} \right.\) 
    Vậy x in {0;1/2;1}

  2. maingocquynhnhu2k1
    maingocquynhnhu2k1
    18 Tháng Mười Một, 2022 at 12:31 chiều
    Reply
    ***Lời giải***
    x^3+(x-1)^3=(2x-1)^3
    <=>x^3+x^3-3x^2+3x-1=8x^3-12x^2+6x-1
    <=>(x^3+x^3-8x^3)+(12x^2-3x^2)+(3x-6x)=-1+1
    <=>-6x^3+9x^2-3x=0
    <=>-3x(2x^2-3x+1)=0
    <=>\(\left[ \begin{array}{l}-3x=0\\2x^2-3x+1=0\end{array} \right.\)
    <=>\(\left[ \begin{array}{l}x=0\\2x^2-2x-x+1=0\end{array} \right.\)
    <=>\(\left[ \begin{array}{l}x=0\\2x(x-1)-(x-1)=0\end{array} \right.\)
    <=>\(\left[ \begin{array}{l}x=0\\(x-1)(2x-1)=0\end{array} \right.\)
    <=>\(\left[ \begin{array}{l}x=0\\x-1=0\\2x-1=0\end{array} \right.\)
    <=>\(\left[ \begin{array}{l}x=0\\x=1\\2x=1\end{array} \right.\)
    <=>\(\left[ \begin{array}{l}x=0\\x=1\\x=\dfrac{1}{2}\end{array} \right.\)
    Vậy S={0;1;1/2}

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

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