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

Toán Lớp 8: Tìm x: x³ – 7x² +14x – 8 = 0 mng giúp mình một câu này thôi ạ!

Toán Lớp 8: Tìm x:
x³ – 7x² +14x – 8 = 0
mng giúp mình một câu này thôi ạ!

Comments ( 2 )

  1. x³ – 7x² + 14x – 8 = 0
    $\Leftrightarrow$ x³ – 1x² – 6x² + 6x + 8x – 8 = 0
    $\Leftrightarrow$ x² ( x – 1 ) – 6x ( x – 1 ) + 8 ( x – 1 ) = 0
    $\Leftrightarrow$ ( x – 1 ) ( x² – 6x + 8 ) = 0
    $\Leftrightarrow$ ( x – 1 ) ( x² – 2x – 4x + 8 ) = 0
    $\Leftrightarrow$ ( x – 1 ) [ x ( x – 2 ) – 4 ( x – 2 ) ] = 0
    $\Leftrightarrow$ ( x – 1 ) ( x – 4 ) ( x – 2 ) = 0
    $\Leftrightarrow$ $\left[\begin{matrix} x – 1 = 0\\ x – 4 = 0\\ x – 2 = 0\end{matrix}\right.$
    $\Leftrightarrow$ $\left[\begin{matrix} x = 1\\ x  = 4\\ x = 2\end{matrix}\right.$

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

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