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

Toán Lớp 8: TÌM X, BIẾT: a. (x+3)^2 – (x-4).(x-8) =1 b. 3(x+2)^2 + (2x-1)^2 – 7(x+3).(x-3) =36 HELP*

Tháng Hai 11, 2023 Toán học 2 Comments 0 views

Toán Lớp 8: TÌM X, BIẾT:
a. (x+3)^2 – (x-4).(x-8) =1
b. 3(x+2)^2 + (2x-1)^2 – 7(x+3).(x-3) =36
HELP*

Comments ( 2 )

  1. lanhuongthu
    lanhuongthu
    11 Tháng Hai, 2023 at 11:14 chiều
    Reply
    bạn xem hình

    toan-lop-8-tim-biet-a-3-2-4-8-1-b-3-2-2-2-1-2-7-3-3-36-help

  2. quynhthanhnhu
    quynhthanhnhu
    11 Tháng Hai, 2023 at 11:14 chiều
    Reply
    a)
    (x+3)^2 – (x-4).(x-8) = 1
    => (x^2 + 2 . x . 3 + 3^2) – (x^2  – 8x – 4x + 32) = 1
    => (x^2 + 6x + 9) – (x^2 – 12x + 32)  = 1
    => x^2 + 6x + 9 – x^2 + 12x – 32 = 1
    => 18x – 23 = 1
    => 18x = 24
    => x = 4/3
    Vậy x = 4/3
    b)
    3 (x+2)^2 + (2x-1)^2 – 7(x+3)(x-3) = 36
    => 3 . (x^2 + 2 . x . 2 + 2^2) + [ (2x)^2 – 2 . 2x . 1 + 1^2] – 7 . (x^2 – 9) = 36
    => 3 . (x^2 + 4x +4) + (4x^2 – 4x + 1) – (7x^2 – 63)  = 36
    => 3x^2 + 12x +12 + 4x^2 – 4x + 1 – 7x^2  + 63 = 36
    => 8x + 76   =36
    => 8x = -40
    => x = -5
    Vậy x = -5
     

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

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