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

Toán Lớp 8: Tìm x biết $(2x-3)^{2}+(2x-1)(2x+1)-(2x+1)$$(4x^{2}-2x+1)+$ $8x^{2}(x-1)=13$

Toán Lớp 8: Tìm x biết
$(2x-3)^{2}+(2x-1)(2x+1)-(2x+1)$$(4x^{2}-2x+1)+$ $8x^{2}(x-1)=13$

Comments ( 2 )

  1. Giải đáp:
     $(2x-3)²+(2x-1).(2x+1)-(2x+1).(4x²-2x+1)+8x².(x-1)=13$
    $⇔ 4x²-12x+9+4x²-1-8x³-1+8x³-8x²=13$
    $⇔ (4x²+4x²-8x²)-12x+(9-1-1)+(8x³-8x³)=13$
    $⇔ -12x+7=13$
    $⇔ -12x= 6$
    $⇔ x= -\dfrac{1}{2}$
     $Vậy$ $x= -\dfrac{1}{2}$

  2. $(2x-3)^2+(2x-1)(2x+1)-(2x+1)(4x^2-2x+1)+8x^2(x-1)=13$
    $4x^2-12x+9+4x^2-1-(8x^3+1)+8x^3-8x^2=13$
    $4x^2-12x+9+4x^2-1-8x^3-1+8x^3-8x^2=13$
    $(4x^2+4x^2-8x^2)-12x+9-2+(-8x^3+8x^3)=13$
    $-12x+7=13$
    $-12x=6$
    $x=\dfrac{6}{-12}$
    $x=\dfrac{-6}{12}$
    $x=\dfrac{-1}{2}$
    Vậy $x=\dfrac{-1}{2}$
    $#thanhmaii2008$

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

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