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

Toán Lớp 8: X^2*(x-3)-12+4x=0 làm giúp mình vs

Toán Lớp 8: X^2*(x-3)-12+4x=0 làm giúp mình vs

Comments ( 2 )

  1. x² x (x – 3) – 12 + 4x = 0
    ⇔ x² x (x – 3) + 4x – 12 = 0
    ⇔ x² x (x – 3) + 4 (x – 3) = 0
    ⇔ (x² + 4) (x – 3) = 0
    ⇔ \(\left[ \begin{array}{l}x^2 + 4=0\\x – 3=0\end{array} \right.\) 
    ⇔ \(\left[ \begin{array}{l}x^2 = -4 (vô lí vì x^2 ≥ 0) \\x = 3\end{array} \right.\) 
                                             Vậy x = 3

  2. $(=) x^3 – 3x^2 – 12 + 4x=0$
    $(=) x^2 (x-3) + 4(-3+x)=0$
    $(=) (x-3) (x^2 + 4)+0$
    $(=) x-3=0$ hoặc $x^2 +4=0$
    $=) x=3$ hoặc x không thuộc R
    =) S = 3

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

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