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Math Help - Variables x and y related by an unconventional type of equation

  1. #1
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    Variables x and y related by an unconventional type of equation

    The variables x and y are related by the equation . When the graph of against is drawn, a straight line is obtained which has a gradient of -5 and passes through the point (-2, 18).

    Find the value of m and n.
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  2. #2
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    Hello fterh
    Quote Originally Posted by fterh View Post
    The variables x and y are related by the equation . When the graph of against is drawn, a straight line is obtained which has a gradient of -5 and passes through the point (-2, 18).

    Find the value of m and n.
    We need to get an expression involving \frac{y}{\sqrt x}, so let's divide both sides by \sqrt x:
    \dfrac{y}{\sqrt x}= m + \dfrac nx
    =n\cdot\dfrac 1x+m
    So when we plot the graph of \frac{y}{\sqrt x} against \frac{1}{x}, the gradient is n. So:
    n=-5
    and if we plug this and the values (-2, 18) into the equation, we get:
    18=(-5)(-2)+m

    \Rightarrow m = 8
    Grandad
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    Genius Thanks grandad
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    Edited: My bad, carless LOL.
    Last edited by fterh; June 19th 2010 at 03:57 AM.
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