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

Toán Lớp 8: Tìm x: (2x-3)² + (x+2) (3-4x) =66

Toán Lớp 8: Tìm x:
(2x-3)² + (x+2) (3-4x) =66

Comments ( 2 )

  1. (2x-3)² + (x+2) (3-4x) =66
    ⇔ (4x² – 12x + 9) + (3x – 4x² + 6 – 8x ) = 66
    ⇔ 4x² -12x + 9 + 3x – 4x² + 6 – 8x = 66
    ⇔ -17x + 15 = 66
    ⇔ -17x = 51
    ⇔ x = -3
     

  2. $\text{( 2x – 3 )² + ( x + 2 )( 3 – 4x ) = 66 }$
    $\text{⇔ 4x² – 12x + 9 + 3x – 4x² + 6 – 8x = 66 }$
    $\text{⇔ ( 4x² – 4x² ) + ( -12x + 3x – 8x ) = 66 – 9 – 6 }$
    $\text{⇔ -17x = 51 }$
    $\text{⇔ x = -3 }$
    $\text{Vậy: x = -3 }$

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

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