SOLUTION: I am really confused on this one. Here is the problem: A child throws a ball up a hill that makes an angle of 45 degrees with the horizontal. The ball lands 100 feet up the hill

Question 727216: I am really confused on this one. Here is the problem:
A child throws a ball up a hill that makes an angle of 45 degrees with the horizontal. The ball lands 100 feet up the hill. Its trajectory is a parabola with equation y= -X^2 + ax for some number a. Find a.
Found 2 solutions by lynnlo, Alan3354:
Answer by lynnlo(4176) (Show Source): You can put this solution on YOUR website!

Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
A child throws a ball up a hill that makes an angle of 45 degrees with the horizontal. The ball lands 100 feet up the hill. Its trajectory is a parabola with equation y= -X^2 + ax for some number a. Find a.
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The hill is the line y = x
100 ft measured on the hill --> x = 100cos(45), y = 100sin(45)
The point of impact is (70.7,70.7)
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y = -x^2 + ax
70.7 = -5000 + a*70.7
a =~ 71.72

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