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

Toán Lớp 8: tìm x : 4(x-1) (x+5)-(x+2) (x+5)=3(x-1) (x+2)

Toán Lớp 8: tìm x : 4(x-1) (x+5)-(x+2) (x+5)=3(x-1) (x+2)

Comments ( 2 )

  1. Giải đáp:
     
    Lời giải và giải thích chi tiết:
    4(x-1)(x+5)-(x+2)(x+5) = 3(x-1)(x+2)
    ⇔ 4(x-1)(x+5) – (x+2)(x+5) =3(x^2+x-2)
    ⇔ 4x^2 + 16x – 20 – x^2 – 7x – 10 = 3x^2 + 3x – 6
    ⇔ (4x^2-x^2) + (16x-7x) – (20+10) = 3x^2 + 3x – 6
    ⇔ 3x^2 + 9x – 30 = 3x^2 + 3x – 6
    ⇔ 3x^2 + 9x = 3x^2 + 3x + 24
    ⇔ 9x = 3x + 24
    ⇔ 6x = 24
    ⇔ x = 4
    Vậy S = {4}

  2. 4(x – 1)(x + 5) – (x + 2)(x + 5) = 3(x – 1)(x + 2)
    ⇔ 4(x^2 + 4x – 5) – (x^2 + 7x + 10) = 3(x^2 + x – 2)
    ⇔ 4x^2 + 16x – 20 – x^2 – 7x – 10 – 3x^2 – 3x + 6 = 0
    ⇔ 6x – 24 = 0
    ⇒ 6x = 24
    ⇒ x = 4
    Vậy  x = 4

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