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Math Help - Direct variation help

  1. #1
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    Direct variation help

    Can some answer these for me please?

    Do the following equations represent direct variations? If so, find the constant of variation

    1. 3x-4y=9
    2. y=1/5y
    3. 8x=4y




    thanks
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  2. #2
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    please .
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  3. #3
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    two variables, y and x, are in a direct variation if y and x can be written in the form y = kx , where k is any constant.
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    Quote Originally Posted by ssppsabres View Post
    please .
    Please do not "bump" your thread. See rule #1 here.

    -Dan
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  5. #5
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    can u answer the question for me tho? Please
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  6. #6
    Forum Admin topsquark's Avatar
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    Look at the first equation. Solve it for y. Is this in the form y = kx? Use the same method for the other two. Post your solution for #1 (or either of the others) so we can see if you err at some point.

    -Dan
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  7. #7
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    y=1.5?
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  8. #8
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    Quote Originally Posted by ssppsabres View Post
    y=1.5?
    how did you get that from the equation 3x - 4y = 9 ?
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  9. #9
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    y=3?
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  10. #10
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    Quote Originally Posted by ssppsabres View Post
    y=3?
    no. you are guessing.

    3x - 4y = 9

    3x - 9 = 4y

    \dfrac{3x}{4} - \dfrac{9}{4} = y

    or

    y = \dfrac{3x}{4} - \dfrac{9}{4}

    now ... is this equation in the form y = kx ?
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  11. #11
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    No, so therefore it is not a DV and has no constant?
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  12. #12
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    So no its not?
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  13. #13
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    Please post complete sentences and show your work.

    Question #1 asked "Do the following equations represent direct variations? If so, find the constant of variation
    1. 3x-4y=9"
    and when asked to post your solution, you posted, in three separate posts,
    "y=1.5? "

    "y=3? "

    "So no its not?"

    The first two make no sense because you were not asked to find a value of y. The last makes no sense because it is not a complete sentence- "so no its not" what?

    Since the questions asks, first whether or not the relation given is a "direct variation", you should start by stating what a direct variatio is and then show how the given relation does or does not satisfy that. If it is a direct variation, then you should give the constant of variation, which is NOT "y".
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