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

Toán Lớp 8: Tìm x i. 2x^{2} + 7x + 6 = 0 k. – x – 10x^{2} + 3 =0

Toán Lớp 8: Tìm x
i. 2x^{2} + 7x + 6 = 0
k. – x – 10x^{2} + 3 =0

Comments ( 2 )

  1. $2x^{2}$ + $7x$ + $6$ $=$ $0$
    $= 2x² + 4x + 3x + 6$
    $= ( 2x + 3 )( x + 2 )$
    ⇔ $x$ $=$ $\frac{3}{2}$ Hay $x$ $=$ $-2$
    $Đáp$ $số$………………….
    $- x – 10x^{2} + 3 =0$
    $10x² + x – 3 = 0$
    $10x – 5x + 6x – 3 = 0$
    $( 5x + 3 )( 2x – 1 ) = 0$
    ⇔  $x$ $=$ $\frac{-3}{5}$ Hay $x$ $=$ $\frac{1}{2}$ 
    $Đáp$ $số$…………

  2. Lời giải và giải thích chi tiết:
    2x² + 7x + 6 = 0
    ⇔ 2x² + 4x + 3x + 6 = 0
    ⇔ 2x( x + 2 + 3( x + 2 ) = 0
    ⇔ ( 2x + 3 )( x + 2 ) = 0
    ⇔ \(\left[ \begin{array}{l}2x+3=0\\x+2=0\end{array} \right.\) 
    ⇔ \(\left[ \begin{array}{l}2x=-3\\x=-2\end{array} \right.\) 
    ⇔ \(\left[ \begin{array}{l}x=\frac{-3}{2}\\x=-2\end{array} \right.\) 
    Vậy x ∈ { $\frac{-3}{2}$ ; -2 }
    -x – 10x² + 3 = 0
    ⇔ -10x² + 5x – 6x + 3 = 0
    ⇔ -5x( 2x – 1 ) – 3( 2x – 1 ) = 0
    ⇔ ( 5x – 3 )( 2x – 1 ) = 0
    ⇔ \(\left[ \begin{array}{l}5x-3=0\\2x-1=0\end{array} \right.\) 
    ⇔ \(\left[ \begin{array}{l}5x=3\\2x=1\end{array} \right.\) 
    ⇔ \(\left[ \begin{array}{l}x=\frac{3}{5}\\x=\frac{1}{2}\end{array} \right.\) 
    Vậy x ∈ { $\frac{3}{5}$ ; $\frac{1}{2}$ }
    CHÚC BẠN HỌC TỐT!

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