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

Toán Lớp 8: Tìm x, biết: a) (8x – 3)(3x + 2) – (4x + 7)(x + 4) = 2(2x + 1)(5x – 1) b) (x – 2)(3x – 4) – 3x(x – 5) = 5x(x – 7) – 5(x – 1)(x + 5)

Home/ Toán Lớp 8: Tìm x, biết: a) (8x – 3)(3x + 2) – (4x + 7)(x + 4) = 2(2x + 1)(5x – 1) b) (x – 2)(3x – 4) – 3x(x – 5) = 5x(x – 7) – 5(x – 1)(x + 5)

Toán Lớp 8: Tìm x, biết: a) (8x – 3)(3x + 2) – (4x + 7)(x + 4) = 2(2x + 1)(5x – 1) b) (x – 2)(3x – 4) – 3x(x – 5) = 5x(x – 7) – 5(x – 1)(x + 5)

Tháng Mười 4, 2022 Toán học 2 Comments 0 views

Toán Lớp 8: Tìm x, biết:
a) (8x – 3)(3x + 2) – (4x + 7)(x + 4) = 2(2x + 1)(5x – 1)
b) (x – 2)(3x – 4) – 3x(x – 5) = 5x(x – 7) – 5(x – 1)(x + 5)

Comments ( 2 )

  1. dananhthumai
    dananhthumai
    4 Tháng Mười, 2022 at 7:02 chiều
    Reply
    Giải đáp:
     
    Lời giải và giải thích chi tiết:
    a) (8x – 3)(3x + 2) – (4x + 7)(x + 4) = 2(2x + 1)(5x – 1)
    ⇔ 24x^2 – 9x + 16x -6 – 4x^2 + 7x + 16x + 28 = (4x +2) ( 5x-1)
    ⇔ 20 x^2 + 30x  + 22 = 20x^2 + 10x -4x-2
    ⇔ 20x^2 + 30x -20x^2 -10x + 4x= -2-22
    ⇔  24x = -24
    ⇔ x  = -1
    Vậy….
    b,  (x – 2)(3x – 4) – 3x(x – 5) = 5x(x – 7) – 5(x – 1)(x + 5)
    ⇔ 3x^2 -6x -4x+8 – 3x^2+ 15x = 5x^2 -35x – [ (5x-1)(x+5)]
    ⇔ 5x + 8 = 5x^2 -35x- ( 5x^2-x+25x-5)
    ⇔ 5x +8 = 5x^2-35x-5x^2+x-25x+5
    ⇔ 5x + 8= -59x +5
    ⇔ 5x + 59x= 5-8
    ⇔ 64x = -3   
    ⇔ x = -64/3
    Vậy…    

  2. minhtamnguyet88
    minhtamnguyet88
    4 Tháng Mười, 2022 at 7:01 chiều
    Reply
    a) (8x – 3)(3x + 2) – (4x + 7)(x + 4) = 2(2x + 1)(5x – 1)
    <=> 24x^2 – 9x + 16x -6 – 4x^2 + 7x + 16x + 28 = (4x +2) ( 5x-1)
    <=> 20 x^2 + 30x  + 22 = 20x^2 + 10x -4x-2
    <=> 20x^2 + 30x -20x^2 -10x + 4x= -2-22
    <=>  24x = -24
    <=> x  = -1
    Vậy S={-1}
    b)  (x – 2)(3x – 4) – 3x(x – 5) = 5x(x – 7) – 5(x – 1)(x + 5)
    <=> 3x^2 -6x -4x+8 – 3x^2+ 15x = 5x^2 -35x – [ (5x-1)(x+5)]
    <=> 5x + 8 = 5x^2 -35x- ( 5x^2-x+25x-5)
    <=> 5x +8 = 5x^2-35x-5x^2+x-25x+5
    <=> 5x + 8= -59x +5
    <=> 5x + 59x= 5-8
    <=>64x = -3
    <=> x = -64/3
    Vậy S={-64/3}

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

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