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

Toán Lớp 8: Bài 1: Tìm x A) 7x(x-3) – (3-x)(5x+1) =0

Home/ Toán Lớp 8: Bài 1: Tìm x A) 7x(x-3) – (3-x)(5x+1) =0

Toán Lớp 8: Bài 1: Tìm x A) 7x(x-3) – (3-x)(5x+1) =0

Tháng Tám 14, 2022 Toán học 2 Comments 0 views

Toán Lớp 8: Bài 1: Tìm x
A) 7x(x-3) – (3-x)(5x+1) =0

Comments ( 2 )

  1. hienchaudiem
    hienchaudiem
    14 Tháng Tám, 2022 at 12:38 sáng
    Reply
    Gửi bạn:
    $7x(x-3)-(3-x)(5x+1)=0$
    $7x(x-3)+(x-3)(5x+1)=0$
    $⇒(x-3)(7x+5x+1)=0$
    $⇒(x-3)(12x+1)=0$
    $⇒$ \(\left[ \begin{array}{l}x-3=0\\12x+1=0\end{array} \right.\) 
    $⇒$ \(\left[ \begin{array}{l}x=3\\x=-\dfrac{1}{12} \end{array} \right.\) 
    Vậy $x=3$ hoặc $x=-\dfrac{1}{12}$
     

  2. catlantuong
    catlantuong
    14 Tháng Tám, 2022 at 12:38 sáng
    Reply
    a)7x(x-3)-(3-x)(5x+1)=0
    <=>-7x.[-(x-3)]-(3-x)(5x+1)=0
    <=>-7x.(3-x)-(3-x)(5x+1)=0
    <=>[-7x-(5x+1)](3-x)=0
    <=>(-7x-5x-1)(3-x)=0
    <=>(-12x-1)(3-x)=0
    <=> \(\left[ \begin{array}{l}-12x-1=0\\3-x=0\end{array} \right.\) 
    <=> \(\left[ \begin{array}{l}-12x=1\\x=3\end{array} \right.\) 
    <=> \(\left[ \begin{array}{l}x=\dfrac{-1}{12}\\x=3\end{array} \right.\) 
    Vậy x∈{(-1)/12;3}

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

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