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Math Help - Parametric equations 3

  1. #1
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    Parametric equations 3

    If I had a parametric equation of x=-5t-3, y=5t+4, t in R, and I needed to specify the position of a moving point P(x,y) at time t, how would I best describe the behavior of the point as t increases?

    1) x decreases, and y decreases.
    2) x decreases, and y increases.
    3) x increases, and y decreases.
    4) x increases, and y increases.
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  2. #2
    MHF Contributor
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    Quote Originally Posted by mike1 View Post
    If I had a parametric equation of x=-5t-3, y=5t+4, t in R, and I needed to specify the position of a moving point P(x,y) at time t, how would I best describe the behavior of the point as t increases?

    1) x decreases, and y decreases.
    2) x decreases, and y increases.
    3) x increases, and y decreases.
    4) x increases, and y increases.
    You assume a value of t that is increased over the t in the equations.
    (I don't have to do that, but you have to, so that you will understand the solution)
    Let us the t in the equations is t=1.
    x = -5*1 -3 = -8
    Then, we increase t, say t = 3,
    x = -5*3 -3 = -18
    So, the x decreases as t increases. -------**

    Do that on the y.
    Old y, when t = 1,
    y = 5t +4
    y = 5*1 +4 = 9
    New y, when t = 3,
    y = 5*3 +4 = 19
    So, the y increases as the t increases. -----**

    Therefore, 2) x decreases, and y increases. -----------answer.
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