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Math Help - Find The Y Intercept - Urgent

  1. #1
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    Unhappy Find The Y Intercept - Urgent

    I need serious help.

    I need to find the Y intercept of the graph

    y= -0.02(x^3 - 38x^2 + 441x - 1620)

    I also need to X when y=3

    I also need to find the equation of the inclined path if it hasa gradient of 4/5

    Please help
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    for the y-intercept, just plug in x = 0
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  3. #3
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    Awesome. Any help with the others?
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  4. #4
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by mibamars View Post
    y= -0.02(x^3 - 38x^2 + 441x - 1620)

    I also need to X when y=3
    y= -0.02(x^3 - 38x^2 + 441x - 1620)

    when y = 3 we have

    3= -0.02(x^3 - 38x^2 + 441x - 1620)

    \Rightarrow x^3 - 38x^2 + 441x - 1470 = 0

    Trying the factors of 1470, we realize that x = 14 is a root, so (x - 14) is a factor. Dividing the cubic by (x - 14) using long division, we obtain:

    x^3 - 38x^2 + 441x - 1470 = (x - 14) \left( x^2 - 24 x + 105 \right) = 0

    \Rightarrow x - 14 = 0 \mbox { or } x^2 - 24x + 105 = 0

    \Rightarrow x = 14 \mbox { or } x = \frac {24 \pm \sqrt {156}}{2}

    Quote Originally Posted by mibamars View Post
    I also need to find the equation of the inclined path if it hasa gradient of 4/5
    when you say inclined path you mean tangent line right?
    Last edited by ThePerfectHacker; July 4th 2007 at 08:05 PM.
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