Question 1197419
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y=-0.005x^2 +x+5  (max at x = 100) y' = 0 ⇒ -.01x + 1 = 0 , x = 100
maximum P(100,55)
what is the maximum height attained by the ball? {{{55ft}}}
Can see from graph travels 'approximately' from -5 to 205 0r  ~210ft 

Recommend using a Graphing software as a visual aid and calculator
FREE graphing software is available at http://www.padowan.dk.com

Below a screenshot of y=-0.005x^2 +x+5  using that software:
Using its 'evaluate' feature can also give a closer approximation to x-intercepts
 *[illustration graph_1021.jpeg].


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