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

Toán Lớp 8: Tìm x $x^{3}$=$\frac{1}{4}$x $x^{3}$ – $2x^{2}$ -4x+8=0 ($x^{2}$ +$9x)^{2}$ -$36x^{2}$ =0

Tháng Chín 16, 2022 Toán học 2 Comments 0 views

Toán Lớp 8: Tìm x
$x^{3}$=$\frac{1}{4}$x
$x^{3}$ – $2x^{2}$ -4x+8=0
($x^{2}$ +$9x)^{2}$ -$36x^{2}$ =0

Comments ( 2 )

  1. hoaiphuong85
    hoaiphuong85
    16 Tháng Chín, 2022 at 1:34 sáng
    Reply
    1)x^3 = 1/4 x $\\$ \Leftrightarrow x^3 – 1/4 x = 0 $\\$ \Leftrightarrow x(x^2 – 1/4 ) = 0 $\\$ \Leftrightarrow x(x-1/2)(x+1/2) = 0 $\\$ \Leftrightarrow [(x= 0),(x-1/2=0),(x+1/2=0):} \Leftrightarrow [(x=0),(x=1/2),(x=-1/2):} $\\$ Vậy : S = {0;1/2;-1/2} $\\$ 2) x^3 – 2x^2 – 4x + 8 = 0 $\\$ \Leftrightarrow x^2(x-2) – 4(x-2) = 0 $\\$ \Leftrightarrow (x-2)(x^2-4) = 0 $\\$ \Leftrightarrow (x-2)^2(x+2) = 0 $\\$ \Leftrightarrow [(x-2=0),(x+2=0):} \Leftrightarrow [(x=2),(x=-2):} $\\$ Vậy : S = {2;-2} $\\$ 3) (x^2 + 9x)^2 – 36x^2 = 0 $\\$ \Leftrightarrow (x^2 + 9x – 6x)(x^2 + 9x + 6x) = 0 $\\$ \Leftrightarrow (x^2+3x)(x^2 + 15x) = 0 $\\$ \Leftrightarrow x^2(x+3)(x+15) = 0 $\\$ \Leftrightarrow [(x=0),(x+3 = 0),(x+15=0):} \Leftrightarrow [(x=0),(x=-3),(x=-15):} $\\$ Vậy : S = {0;-3;-15}

  2. truongankimtrong
    truongankimtrong
    16 Tháng Chín, 2022 at 1:34 sáng
    Reply
    Giải đáp + Lời giải và giải thích chi tiết:
    x^3=1/4x
    <=>x^3-1/4x=0
    <=>x(x^2-1/4)=0
    <=>x(x-1/2)(x+1/2)=0
    <=>\(\left[ \begin{array}{l}x=0\\x-\dfrac{1}{2}=0\\x+\dfrac{1}{2}=0\end{array} \right.\)
    <=>\(\left[ \begin{array}{l}x=0\\x=\dfrac{1}{2}\\x=-\dfrac{1}{2}\end{array} \right.\)
    Vậy S={0;1/2;-1/2}
    x^3-2x^2-4x+8=0
    <=>x^2(x-2)-4(x-2)=0
    <=>(x-2)(x^2-4)=0
    <=>(x-2)(x-2)(x+2)=0
    <=>[(x-2=0),(x-2=0),(x+2=0):}
    <=>[(x=2),(x=2),(x=-2):}<=>[(x=2),(x=-2):}
    Vậy S={2;-2}
    (x^2+9x)^2-36x^2=0
    <=>(x^2+9x)^2-(6x)^2=0
    <=>(x^2+9x-6x)(x^2+9x+6x)=0
    <=>(x^2+3x)(x^2+15x)=0
    <=>x(x+3)*x(x+15)=0
    <=>x^2(x+3)(x+15)=0
    <=>[(x^2=0),(x+3=0),(x+15=0):}
    <=>[(x=0),(x=-3),(x=-15):}
    Vậy S={0;-3;-15}.
     

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

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