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Math Help - Two PRE-Calc ?'s

  1. #1
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    Two PRE-Calc ?'s

    1. Suppose you have to use exactly 200 m of fencing to make either one square enclosure or two seperate square enclosures of any sizes you wish. What plan gives you the least area? The greatest area?



    2. If a ball is thrown upward from a building 30m tall and the ball has a vertical velocity of 25m/s, then its approximate height above the ground t seconds later is fiven by h(t)=30=25t-5t^2
    a.) after how many seconds does the ball hit the ground?
    b.) what is the domain of h?
    c.) How high does the ball go




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  2. #2
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    Hello,
    Quote Originally Posted by ep78 View Post
    1. Suppose you have to use exactly 200 m of fencing to make either one square enclosure or two seperate square enclosures of any sizes you wish. What plan gives you the least area? The greatest area?
    - if you decide to make one square, the length of a side will be 200/4=50. Thus the area is 50=2500m.
    - if you decide to make two squares. Let x the length of fencing used for the first square. The second square will be 200-x.
    x/4 and (200-x)/4 will be the lengths of the sides of each square.
    Thus their added area will be :
    \frac{x^2}{16}+\frac{(200-x)^2}{16}=\frac{x^2+40000+x^2-400x}{16}=\frac{x^2-200+20000}{8}

    Note that 0 \le x \le 200 and find the maximum of x^2-200+20000


    2. If a ball is thrown upward from a building 30m tall and the ball has a vertical velocity of 25m/s, then its approximate height above the ground t seconds later is fiven by h(t)=30=25t-5t^2
    a.) after how many seconds does the ball hit the ground?
    Solve for t in h(t)=0, since when the ball hits the ground, its height is 0.

    b.) what is the domain of h?
    Well, you can do it
    c.) How high does the ball go
    Find the maximum
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