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

Toán Lớp 8: TÌM X BIẾT 1) 2x ² + 3(x – 1)(x + 1) = 5x(x + 1) 2) (x + 3)(x – 3) – (x – 2)(x + 5) = 6

Toán Lớp 8: TÌM X BIẾT
1) 2x ² + 3(x – 1)(x + 1) = 5x(x + 1)
2) (x + 3)(x – 3) – (x – 2)(x + 5) = 6

Comments ( 2 )

  1. Giải đáp + Lời giải và giải thích chi tiết:
    a, 2x^1+3(x-1)(x+1)=5x(x+1)
    ⇔2x^2+3(x^2-1)-5x(x+1)=0
    ⇔2x^2+3x^2-3-5x^2-5x=0
    ⇔-5x=3
    ⇔x=-3/5
    b, (x+3)(x-3)-(x-2)(x+5)=6
    ⇔(x^2-9)-(x^2+5x-2x-10)=6
    ⇔x^2-9-x^2-3x+10=6
    ⇔-3x=5
    ⇔x=-5/3

  2. 1) 2x ² + 3(x – 1)(x + 1) = 5x(x + 1)
    <=>2x ² + 3(x^2-1) = 5x^2 + 5x
    <=>2x ² + 3x^2-3 – 5x^2 – 5x=0
    <=>-5x-3=0
    <=>-5x=3
    <=>x=-3/5
    Vậy x=-3/5
    2) (x + 3)(x – 3) – (x – 2)(x + 5) = 6
    <=>x^2-9-(x^2+5x-2x-10)-6=0
    <=>x^2-9-x^2-5x+2x+10-6=0
    <=>-3x-5=0
    <=>-3x=5
    <=>x-5/3
    Vậy x=-5/3
     

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

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