Math

I need help solving this using the substitution method
4p-2q= 16,
5p + 7q= 1

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  1. 19-7-5=

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    posted by amanda
  2. Start with one formula.

    4p - 2q = 16

    Get one variable alone on one side of the equation.

    -2q = 16 - 4p

    q = 2p - 8

    Then substitute the value into the other equation.

    5p + 7q = 1

    5p + 7(2p - 8)= 1

    Solve for p.

    Once you find p, put that value into the first equation to solve for q. To check, put both values back into the second equation.

    I hope this helps. Thanks for asking.

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    posted by PsyDAG
  3. 4 p = 16 + 2 q
    so
    p = (4 + .5 q)
    substitute that value for p in the second equation
    5 (4 + .5 q) + 7 q = 1
    20 + 2.5 q + 7 q = 1
    9.5 q = -19
    q = -190/95 = -38/19 =-2
    put that back in either first or second equation to solve for p
    p = 4 + .5*(-2)
    p = 4 - 1 = 3


    check
    4(3) -2 (-2) = 12 + 4 = 16 check
    5(3) + 7(-2) = 15 - 14 = 1 check

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    posted by Damon

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