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

Toán Lớp 8: tìm x (x^2+2x+1)/((x-3)(x+3))=6

Tháng Mười Hai 30, 2022 Toán học 1 Comment 0 views

Toán Lớp 8: tìm x
(x^2+2x+1)/((x-3)(x+3))=6

Comments ( 1 )

  1. dantam45
    dantam45
    30 Tháng Mười Hai, 2022 at 8:37 sáng
    Reply
    $\text{Giải đáp:}$    $\text{ĐKXĐ:x\neq±3}$
    $$\dfrac{x^2+2x+1}{(x-3)(x+3)}=6$$
    $$⇔\dfrac{(x+1)^2}{x^2-9}=6$$
    $$⇔(x+1)^2=6x^2-54$$
    $$⇔x^2+2x+1-6x^2+54=0$$
    $$⇔-5x^2+2x+55=0$$
    $$⇔-5(x^2-\dfrac{2}{5}x)+55=0$$
    $$⇔-5(x^2-\dfrac{2}{5}x+(\dfrac{1}{5})^2-(\dfrac{1}{5})^2)+55=0$$
    $$⇔-5(x-\dfrac{1}{5})^2+\dfrac{276}{5}=0$$
    $$⇔(x-\dfrac{1}{5})^2=\dfrac{276}{25}$$
    $$⇔\left[ \begin{array}{l}x-\dfrac{1}{5}=\sqrt{\dfrac{276}{25}}\\ x-\dfrac{1}{5}=-\sqrt{\dfrac{276}{25}}  \end{array} \right.$$
    $$⇔\left[ \begin{array}{l}x=\sqrt{\dfrac{276}{25}}+\dfrac{1}{5}\\ x=-\sqrt{\dfrac{276}{25}}+\dfrac{1}{5}  \end{array} \right.$$
    $\text{Vậy…………}$
     

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

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