Simultaneous Equation challenge.?

4x + y = 25

x - 3y = 16

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  • 5 years ago
    Favorite Answer

    ...

    4x + y = 25

    x - 3y = 16

    multiply 1st equation by 3

    12x + 3y = 75

    x - 3y = 16

    now add them

    13x = 91

    x = 7

    then

    4x + y = 25

    28 + y = 25

    so

    y = -3

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  • 5 years ago

    4x + y = 25; y = 25 - 4x. Substitute for y in equation 2...

    x - 3(25 - 4x) = 16

    x - 75 + 12x = 16

    13x - 75 = 16

    13x = 91

    x = 7. Substitute for x in equation 1...

    4(7) + y = 25

    28 + y = 25

    y = -3.

    The solution is (7, -3).

  • Como
    Lv 7
    5 years ago

    12x + 3y = 75

    x - 3y = 16

    13x = 91

    x = 7

    28 + y = 25

    y = - 3

    x = 7 , y = - 3

  • 5 years ago

    4x + y = 25

    x - 3y = 16

    Multiply the top eq'n by '3'

    Hence

    12x + 3y = 75

    x - 3y = 16

    Add

    13x = 91

    x = 7

    When x = 7

    4(7) + y = 25

    28 + y = 25

    y = -3

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  • ?
    Lv 7
    5 years ago

    4x + y = 25

    x - 3y = 16

    13x =91

    x = 7, y = -3

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