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Math Help - Maths Homework.

  1. #1
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    Maths Homework.

    The height s metres of a mass thrown vertically upward at a time t seconds given by

    S=40t-13t2

    Show when 25m= 40t - 13t2, 13t2 - 40t + 25 = 0

    There is something about what you do to one side you have to do to the other?
    Last edited by HollieMay2600; March 20th 2012 at 04:27 AM.
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  2. #2
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    Re: Maths Homework.

    What is m?
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  3. #3
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    Re: Maths Homework.

    Quote Originally Posted by Prove It View Post
    What is m?
    m is metres
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    Re: Maths Homework.

    Quote Originally Posted by HollieMay2600 View Post
    Show when 25m= 40t - 13t2, - 13t2 - 40t + 25 = 0

    There is something about what you do to one side you have to do to the other?
    I suppose that this represents system of two equations :

    (1) : -13t_2+40t-25=0

    (2) : -13t_2-40t+25=0

    (1)+(2) : -26t_2=0 \Rightarrow t_2=0

    hence :

    40t=25 \Rightarrow t=\frac{5}{8}
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  5. #5
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    Re: Maths Homework.

    Quote Originally Posted by princeps View Post
    I suppose that this represents system of two equations :

    (1) : -13t_2+40t-25=0

    (2) : -13t_2-40t+25=0
    No. This should be 13t^2- 40t+ 25= 0 which has, by the quadratic formula, solutions
    \frac{40\pm\sqrt{1600+ 1300}}{26}= \frac{40\pm\sqrt{2900}}{26}.

    (1)+(2) : -26t_2=0 \Rightarrow t_2=0

    hence :

    40t=25 \Rightarrow t=\frac{5}{8}
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  6. #6
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    Re: Maths Homework.

    Yes it is clear now , after original post is edited .
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