Tuesday, June 30, 2015

Simultaneous equation practice with Kramer's rule


6x + 5y = 18
2x - y = -4

3x + 7y = 12
2x + 5y = -18

Answers in the comments.
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1 comment:

  1. Prof. HubbardJune 30, 2015 at 7:53 PM

    6x + 5y = 18
    2x - y = -4

    First determinant (denominator)

    | 6 5|
    | 2 -1| = -6 -10 = -16

    Swap out x column

    | 18 5|
    | -4 -1| = -18 +20 = 2


    Swap out y column

    | 6 18|
    | 2 -4| = -24 - 36 = -60

    So x = 2/-16 = -1/8
    and y = -60/-16 = 15/4 = 3 3/4


    =========

    3x + 7y = 12
    2x + 5y = -18

    First determinant (denominator)

    | 3 7|
    | 2 5| = 15 - 14 = 1

    Swap out x column

    | 12 7|
    | -18 5| = 60 + 126 = 186


    Swap out y column

    | 3 12|
    | 2 -18| = -54 - 24 = -78

    So x = 186/1 = 186
    and y = -78/1 = -78


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