Giúp mình câu 4 với cảm ơn mn :((

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Giúp mình câu 4 với cảm ơn mn :((
giup-minh-cau-4-voi-cam-on-mn

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Adela 4 years 2020-10-29T20:01:39+00:00 1 Answers 72 views 0

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  1. Tryphena
    0
    2020-10-29T20:03:05+00:00
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    Đáp án:

    $\begin{array}{l}
    a)14{x^2}y – 21x{y^2} + 28{x^2}{y^2}\\
     = 7xy\left( {2x – 3y + 4xy} \right)\\
    b)27{x^3} – \dfrac{1}{{27}}\\
     = {\left( {3x} \right)^3} – {\left( {\dfrac{1}{3}} \right)^3}\\
     = \left( {3x – \dfrac{1}{3}} \right)\left( {9{x^2} + 3x.\dfrac{1}{3} + \dfrac{1}{9}} \right)\\
     = \left( {3x – \dfrac{1}{3}} \right)\left( {9{x^2} + x + \dfrac{1}{9}} \right)\\
    c)3{x^2} – 3xy – 5x + 5y\\
     = 3x\left( {x – y} \right) – 5\left( {x – y} \right)\\
     = \left( {x – y} \right)\left( {3x – 5} \right)\\
    d){x^2} + 7x + 12\\
     = {x^2} + 3x + 4x + 12\\
     = \left( {x + 3} \right)\left( {x + 4} \right)
    \end{array}$

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