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14 December, 20:46

5x + 6y = 18 and 18x - 15y = 36

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Answers (2)
  1. 14 December, 22:11
    0
    5x+6y=18

    5x=18-6y

    x = (18-6y) / 5

    Use that in the other equation

    18 (18-6y) / 5 - 15y = 36

    64.8-21.6y - 15y = 36

    28.8=36.6y

    .7868=y

    Now put that number in for y on the first equation

    5x+6 (.78) = 18

    5x + 4.68 = 18

    5x = 13.32

    x = 2.66

    and y =.78
  2. 14 December, 22:13
    0
    Solution : {x, y, z} = {-3,-2,-1} System of Linear Equations entered : [1] x + 6y + 3z = - 18 [2] - x + 6y - 3z = - 6 [3] 5x - 6y + 3z = - 6 Solve by Substitution:

    / / Solve equation [1] for the variable x

    [1] x = - 6y - 3z - 18

    / / Plug this in for variable x in equation [2]

    [2] - (-6y-3z-18) + 6y - 3z = - 6 [2] 12y = - 24

    / / Plug this in for variable x in equation [3]

    [3] 5• (-6y-3z-18) - 6y + 3z = - 6 [3] - 36y - 12z = 84

    / / Solve equation [2] for the variable y

    [2] 12y = - 24 [2] y = - 2

    / / Plug this in for variable y in equation [3]

    [3] - 36• (-2) - 12z = 84 [3] - 12z = 12

    / / Solve equation [3] for the variable z

    [3] 12z = - 12 [3] z = - 1

    / / By now we know this much:

    x = - 6y-3z-18 y = - 2 z = - 1

    / / Use the y and z values to solve for x

    x = - 6 (-2) - 3 (-1) - 18 = - 3

    Solution : {x, y, z} = {-3,-2,-1} Processing ends successfully
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