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Math Help - Tricky solution set.

  1. #1
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    Question Tricky solution set.

    The solution set for the equation: x - 4 - square root of(9x) = 0 consists of:


    A) exactly one negative number
    B) exactly one positive number ---Answer
    C) exactly on positive number and one negative number.
    D) exactly two negative numbers.
    E) exactly two positive.


    B) is the answer, but I have no idea why and neither does my dad, can someone please help me with this?
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  2. #2
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    are you sure?

    Are you positive that there is only one positive answer? because I got two positive answers. x=16 and x=1
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  3. #3
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    well...

    It says that question 25.'s (this question) answer is B.

    So I'm pretty sure... but could you show me what you did? Because I didn't even get that close to an answer.

    Thanks for the speedy reply.


    Edit: Nevermind I get what you did! 1 doesn't work because 1-4-3= -6 not 0

    so can you show me how you got 16 ?
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  4. #4
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    solution?

    Sure,

    x - 4 - sqrt(9x) = 0 add sqrt(9x) to both sides
    x - 4 = sqrt(9x) now square both sides
    x^2 - 8x + 16 = 9x subtract 9x from both sides
    x^2 - 17x + 16 = 0 factor the left hand side
    (x - 16) (x - 1) = 0 set both values equal to 0
    x = 16 x = 1
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  5. #5
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    woops

    I didn't even remember to check the answers. good job, there's your answer. 16 works, but not 1
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  6. #6
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    Thanks!!!

    I forgot one of the most basic things in Algebra, gosh I feel dumb.


    Thank you!!
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