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

Toán Lớp 9: giải phương trình : x^2 – 3x + 5 = căn 6x – 3

Toán Lớp 9: giải phương trình : x^2 – 3x + 5 = căn 6x – 3

Comments ( 1 )

  1. x^2 – 3x + 5 = sqrt(6x – 3)
    ⇒ sqrt(6x – 3) = x^2−3x+5
    ⇒ sqrt(6x – 3) = (x^2−3x+5)^2
    ⇒ 6x−3=x^4−6x^3+19x^2−30x+25
    ⇒ 6x−3−(x^4−6x^3+19x^2−30x+25)=x^4−6x^3+19x^2−30x+25−(x^4−6x^3+19x^2−30x+25)
    ⇒ −x^4+6x^3−19x^2+36x−28=0
    ⇒ (−x+2)(x−2)(x^2−2x+7)=0
    ⇒ \(\left[ \begin{array}{l}−x+2=0\\x^2−2x+7=0\end{array} \right.\)
    ⇒ \(\left[ \begin{array}{l}x=2\\x=2\end{array} \right.\) 
    Vậy S = {2}.
     

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

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