Giúp em làm bài 30 với ạ ❤️

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Giúp em làm bài 30 với ạ ❤️
giup-em-lam-bai-30-voi-a-️

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Orla Orla 4 years 2020-10-30T02:33:11+00:00 2 Answers 8 views 0

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  1. Acacia
    0
    2020-10-30T02:34:25+00:00
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    a) $(x+3)(x^2-3x+9)-(5x+x^3)$

    $=(x+3)(x^2-3x+3^2)-5x-x^3$

    $=x^3+3^3-5x-x^3$

    $=27-5x$

    b) $(2x+y)(4x^2-2xy+y^2)-(2x-y)(4x^2+2xy+y^2)$

    $=(2x+y)[(2x)^2-2x.y+y^2]-(2x-y)[(2x)^2+2x.y+y^2]$

    $=(2x)^3+y^3-[(2x)^3-y^3]$

    $=8x^3+y^3-8x^3+y^3$

    $=2y^3$

     

  2. giahuy
    0
    2020-10-30T02:35:03+00:00
    Reply

    Đáp án:

    $a, (x + 3)(x² – 3x + 9) – (54 + x³) $

    $= x³ + 3³ – 54 – x³ $

    $= x³ + 27 – 54 – x³ $

    $= -27$

    $b, (2x + y)(4x² – 2xy + y²) – (2x – y)(4x² + 2xy + y²)$

    $= (2x)³ + y³ – [(2x)³ – y³]$

    $= 8x³ + y³ – (8x³ – y³) $

    $= 8x³ + y³ – 8x³ + y³ $

    $= 2y³ $

     

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Giải phương trình 1 ẩn: x + 2 - 2(x + 1) = -x . Hỏi x = ? ( )