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

Toán Lớp 8: Giá trị của x thỏa mãn (10x+9).x-(5x-1)(2x+3)=8 là

Toán Lớp 8: Giá trị của x thỏa mãn (10x+9).x-(5x-1)(2x+3)=8 là

Comments ( 2 )

  1. $\text{( 10x + 9 )x – ( 5x – 1 )( 2x + 3 ) = 8}$
    $\text{⇔ 10$x^{2}$ + 9x – ( 10$x^{2}$ + 15x – 2x – 3 ) = 8}$
    $\text{⇔ 10$x^{2}$ + 9x – ( 10$x^{2}$ + 13x – 3 ) = 8}$
    $\text{⇔ 10$x^{2}$ + 9x – 10$x^{2}$ – 13x + 3 = 8}$
    $\text{⇔ 9x – 13x + 3 = 8}$
    $\text{⇔ -4x + 3 = 8}$
    $\text{⇔ -4x = 5}$
    $\text{⇔ x = -}$$\dfrac{5}{4}$
    Vậy $\text{x = -}$$\dfrac{5}{4}$

  2. $Đáp$ $án:$
     $(10x+9).x-(5x-1).(2x+3)=8$
    $⇔ 10x²+9x-10x²-13x+3=8$
    $⇔ (10x²-10x²)+(9x-13x)+3=8$
    $⇔ -4x+3=8$
    $⇔-4x=5$
    $⇔ x=$$-\frac{5}{4}$ 
     $Vậy$ $x=$$-\frac{5}{4}$
    $FESTIVALS$

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