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

Toán Lớp 8: Bài 1:Tìm x biết: a)2x^3+2x+x^2+1=0 b)(x-2)^2-(x-3)(x+3)=6 c)(2x-1)^2-25=0

Toán Lớp 8: Bài 1:Tìm x biết:
a)2x^3+2x+x^2+1=0
b)(x-2)^2-(x-3)(x+3)=6
c)(2x-1)^2-25=0

Comments ( 2 )

  1. Cho mình xin 5 sao nha bạn
    #Lùn
    toan-lop-8-bai-1-tim-biet-a-2-3-2-2-1-0-b-2-2-3-3-6-c-2-1-2-25-0

  2. Lời giải và giải thích chi tiết:
    a)2x^3 +2x+x^2 +1=0
    <=>2x(x^2 +1)+x^2 +1=0
    <=>(x^2 +1)(2x+1)=0
    <=> \(\left[ \begin{array}{l}x^2+1=0\\2x+1=0\end{array} \right.\) 
    <=> \(\left[ \begin{array}{l}x\notin\mathbb{R}\\x=-\dfrac{1}{2}\end{array} \right.\) 
    Vậy x∈{-1/2}
    b)(x-2)^2 -(x-3)(x+3)=6
    <=>x^2 -4x+4-(x^2 -9)=6
    <=>x^2 -4x+4-x^2 +9=6
    <=>-4x+13=6
    <=>-4x=-7
    <=>x=7/4
    Vậy x∈{7/4}
    c)(2x-1)^2 -25=0
    <=>(2x-1-5)(2x-1+5)=0
    <=>(2x-6)(2x+4)=0
    <=>2(x-3).2(x+2)=0
    <=>(x-3)(x+2)=0
    <=> \(\left[ \begin{array}{l}x-3=0\\x+2=0\end{array} \right.\) 
    <=> \(\left[ \begin{array}{l}x=3\\x=-2\end{array} \right.\) 
    Vậy x∈{-2;3}

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

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