Câu 4 nha

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Câu 4 nha
cau-4-nha

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Nem 4 years 2020-10-14T08:08:02+00:00 1 Answers 132 views 0

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  1. Acacia
    0
    2020-10-14T08:09:11+00:00
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    Đáp án:

    Ta có : 

    `3a^2 + 3b^2 = 10ab`

    `<=> 3a^2 – 10ab + 3b^2 = 0`

    `<=> 3a^2 – 9ab – (ab – 3b^2) = 0`

    `<=> 3a(a – 3b) – b(a – 3b) = 0`

    `<=> (3a – b)(a – 3b) = 0`

    <=> \(\left[ \begin{array}{l}b = 3a\\a = 3b\end{array} \right.\) 

    TH1 : `b = 3a`

    `Q = a^2/b^2 – b^2/a^2`

    `= a^2/(3a)^2 – (3a)^2/a^2`

    `= a^2/(9a^2) – (9a^2)/a^2`

    `= 1/9 – 9`

    `= 1/9 – 81/9`

    `= -80/9`

    TH2 : `a = 3b`

    `=> Q = a^2/b^2 – b^2/a^2`

    `= (3b)^2/b^2 – b^2/(3b)^2`

    `= (9b^2)/b^2 – b^2/(9b^2)`

    `= 9 – 1/9`

    `= 81/9 – 1/9`

    `= 80/9`

    Giải thích các bước giải:

     

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