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Math Help - Need some help please!

  1. #1
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    Need some help please!

    1.Use test points within the intervals formed by the x-intercepts to determine the sign of f(x) in the interval.
    f(x)= 2x^3+x^2-8x-4 How do you find the test points?

    2.f(x)= 2x+3/3x^2+x-6 Same goes for this problem as stated above.

    3.For a body falling freely from rest ,the distance the body falls varies directly as the square of the time. If an object is dropped from a tower 400 ft high and hits the ground in 5 seconds, how far did it fall in the first 3 seconds?

    4.The volume of wood V in a tree varies jointly as the height H and the square of the girth G. (girth is the distance around the tree.) If the volume of a redwood tree is 216m^3 when the height is 30 m and the girth is 1.5 m, what is the height of a tree whose volume is 960m^3 and girth is 2 m?

    5.Explain how the graph of f(x) = -2/(x-3)^2can be obtained from the graph of y= 1/x^2 by means of translations, compressions, expansions, or reflections.


    Any help on these please??
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  2. #2
    Junior Member
    Joined
    Feb 2013
    From
    Australia
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    Re: Need some help please!

    For 3) Use s = ut + 0.5at^2 with u = 0, t =5 ,s = 400 ft = 121.92 m to find a ( it appears to not be 9.81 in this case) then substitute t = 3 into s = 0.5at^2

    5) f(x) is y translated +3 units in the x direction, expanded with scale factor 2 and reflected in the x axis.
    Last edited by Vishak; March 6th 2013 at 12:40 AM.
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