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

Toán Lớp 8: Bài 1 tìm x a) ( 2x + 5 )² – ( x + 2 )² = 0 b)( x + 1 )( 7x + 2 )- 2x² – 4x – 2 = 0

Tháng Mười Hai 28, 2022 Toán học 2 Comments 0 views

Toán Lớp 8: Bài 1 tìm x
a) ( 2x + 5 )² – ( x + 2 )² = 0
b)( x + 1 )( 7x + 2 )- 2x² – 4x – 2 = 0

Comments ( 2 )

  1. lanhuongthu
    lanhuongthu
    28 Tháng Mười Hai, 2022 at 2:24 chiều
    Reply
    Đáp án:
     
    Giải thích các bước giải:
     

    toan-lop-8-bai-1-tim-a-2-5-2-0-b-1-7-2-2-4-2-0

  2. thanhtung
    thanhtung
    28 Tháng Mười Hai, 2022 at 2:23 chiều
    Reply
    a) (2x + 5)^2 – (x + 2)^2 = 0
    => (2x + 5 + x + 2)(2x + 5 – x – 2) = 0
    => (3x + 7)(x + 3) = 0
    => \(\left[ \begin{array}{l}3x + 7 = 0\\x + 3 = 0\end{array} \right.\) 
    => \(\left[ \begin{array}{l}3x = -7 => x = \dfrac{-7}{3}\\x = -3\end{array} \right.\)
    b) (x + 1)(7x + 2) – 2x^2 – 4x – 2 = 0
    => 7x^2 + 2x + 7x + 2 – 2x^2 – 4x – 2 = 0
    => (7x^2 – 2x^2) + (2x – 4x + 7x) (2 – 2) = 0
    => 5x^2 + 5x = 0
    => x(5x + 5) = 0
    => \(\left[ \begin{array}{l}x = 0\\5x + 5 = 0 => 5x = -5 => x = -1\end{array} \right.\)  
       
       
     

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

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