What was Dimitri’s mistake? He mixed up the coordinates of the ordered pair when Substituting it into the equations 7x+9y=-4 and 5x-2y=6

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What was Dimitri’s mistake? He mixed up the coordinates of the ordered pair when Substituting it into the equations 7x+9y=-4 and 5x-2y=6

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Thiên Thanh 3 years 2021-08-26T10:22:56+00:00 1 Answers 22 views 0

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  1. thanhcong
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    2021-08-26T10:24:04+00:00
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    Answer:

    He made a mistake in his calculations when simplifying 5x – 2y

    Step-by-step explanation:

    Given

    The coordinate pair

    (x,y) = (2,-2)

    The equations

    7x + 9y = ?

    5x - 2y = ?

    Dimitri’s Solution

    Equation\ 1: 7x + 9y = -4.

    7(2) + 9 (-2) = -4.

    14 + (-18) = -4.

    -4 = -4.

    Equation\ 2: 5x -2y = 6.

    5(2) - 2 (-2) = 6.

    10 - 4 = 6.

    6 = 6.

    Required

    Identify Dimitri’s mistake

    In the first equation, Dimitri made no mistake.

    However, he made a mistake when simplifying the second equation.

    We have:

    5x - 2y

    and

    (x,y) = (2,-2)

    Substitute x = 2 and y = -2

    So, we have:

    5(2) -2(-2)

    Open bracket

    10 +4

    Finally, we have:

    14

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