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

Toán Lớp 10: Giải phương trình căn 3 x bình – 8 x + 30 = 8 – 3x

Toán Lớp 10: Giải phương trình căn 3 x bình – 8 x + 30 = 8 – 3x

Comments ( 2 )

  1. \sqrt{(3x)^2} – 8x + 30 = 8-3x
    <=>|3x| -8x + 30 = 8-3x
    <=> |3x| = -8x + 30 – 8 + 3x
    <=> |3x| = -5x + 22
    <=> \(\left[ \begin{array}{l}3x=-5x+22\\3x=5x-22\end{array} \right.\) 
    <=> \(\left[ \begin{array}{l}8x=22\\2x=22\end{array} \right.\) 
    <=> \(\left[ \begin{array}{l}x=2,75\\x=11\end{array} \right.\) 
    Vậy S={2,75;11}

  2.      $\sqrt{(3x)²}$ – 8x + 30 = 8 – 3x
    ⇔ | 3x | – 8x + 30 = 8 – 3x
    ⇔ | 3x | = 8x – 3x – 30 + 8
    ⇔ | 3x | = 5x – 22
    ⇔ $\left[\begin{matrix} 3x = 5x – 22 \\ 3x = -5x + 22 \end{matrix}\right.$
    ⇔ $\left[\begin{matrix} 2x = 22 \\ 8x = 22 \end{matrix}\right.$
    ⇔ $\left[\begin{matrix} x = 11 \\ x = 2,75 \end{matrix}\right.$
     Vậy x = 11 hoặc x = 2,75

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

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