cho x/2=y/5=z/7 tính A=x-y+z/x+2y-z

Question

cho x/2=y/5=z/7
tính A=x-y+z/x+2y-z

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Khang Minh 9 months 2020-10-29T02:25:44+00:00 1 Answers 85 views 0

Answers ( )

    0
    2020-10-29T02:27:11+00:00

    Đáp án:

    \[A = \dfrac{4}{5}\]

    Giải thích các bước giải:

     Đặt \(\dfrac{x}{2} = \dfrac{y}{5} = \dfrac{z}{7} = a\), ta có:

    \(\begin{array}{l}
    \dfrac{x}{2} = \dfrac{y}{5} = \dfrac{z}{7} = a \Rightarrow \left\{ \begin{array}{l}
    x = 2a\\
    y = 5a\\
    z = 7a
    \end{array} \right.\\
    A = \dfrac{{x – y + z}}{{x + 2y – z}} = \dfrac{{2a – 5a + 7a}}{{2a + 2.5a – 7a}} = \dfrac{{4a}}{{5a}} = \dfrac{4}{5}
    \end{array}\)

    Vậy \(A = \dfrac{4}{5}\)

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