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

Toán Lớp 8: Giúp mik với Tìm x 2x³ – x² + 2x – 1= 0

Toán Lớp 8: Giúp mik với
Tìm x
2x³ – x² + 2x – 1= 0

Comments ( 2 )

  1. 2x^3 – x^2 + 2x – 1 = 0
    <=> (2x^3+2x) – (x^2+1) =0
    <=> 2x(x^2+1) – (x^2+1) = 0
    <=> (2x-1)(x^2+1)=0
    <=> \(\left[ \begin{array}{l}2x-1=0\\x^2+1=0\end{array} \right.\) 
    <=> \(\left[ \begin{array}{l}2x=1\\x^2+1=0(L)\end{array} \right.\) 
    <=> x = 1/2
    Vậy x = 1/2

  2. 2x^3 – x^2 + 2x – 1= 0
    <=> (2x^3 – x^2) + (2x – 1)= 0
    <=> x^2 (2x – 1) + (2x – 1)= 0
    <=> (x^2 + 1) (2x-1) = 0
    <=> \(\left[ \begin{array}{l}x^2 + 1 = 0\\2x-1 = 0\end{array} \right.\)
    <=> \(\left[ \begin{array}{l}x^2 = -1 (Vô Lý)\\x =\frac{1}{2} \end{array} \right.\) 
    Vậy x = 1/2 thì 2x^3 – x^2 + 2x – 1= 0
     

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

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