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

Toán Lớp 8: Tìm x 2x^3 – x^2 − 13x − 6 = 0

Toán Lớp 8: Tìm x
2x^3 – x^2 − 13x − 6 = 0

Comments ( 2 )

  1. Giải đáp + Lời giải và giải thích chi tiết:
    $#hyn$
    $2x^3-x^2-13x-6=0$
    $⇒2x^3+x^2-2x^2-x-12x-6=0$
    $⇒x^2(2x+1)-x(2x+1)-6(2x+1)=0$
    $⇒(2x+1)(x^2-x-6)=0$
    $⇒(2x+1)(x^2+2x-3x-6)=0$
    $⇒(2x+1)(x+2)(x-3)=0$
    $⇒x=$ $\frac{-1}{2}$ hoặc $x=-2$ hoặc $x=3$  
     

  2. 2x^3-x^2-13x-6=0
    <=>2x^3+x^2-2x^2-x-12x-6=0
    <=> x^2(2x+1)-x(2x+1)-6(2x+1)=0
    <=>(x^2-x-6)(2x+1)=0
    <=>(x^2-3x+2x-6)(2x+1)=0
    <=>[x(x-3)+2(x-3)](2x+1)=0
    <=>(x+2)(x-3)(2x+1)=0
    <=> \(\left[ \begin{array}{l}x+2=0\\x-3=0\\2x+1=0\end{array} \right.\) <=>\(\left[ \begin{array}{l}x=-2\\x=3\\x=\dfrac{-1}{2}\end{array} \right.\) 
    vậy S={-2;3-1/2}

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