SOLUTION: An astronaut on the moon throws a baseball upward. The height of the ball in feet (y) is related to the number of seconds since the ball was thrown (x). y=-2.7x^2+30x+6.5 A. How

Algebra ->  Finance -> SOLUTION: An astronaut on the moon throws a baseball upward. The height of the ball in feet (y) is related to the number of seconds since the ball was thrown (x). y=-2.7x^2+30x+6.5 A. How      Log On


   

Question 1100432: An astronaut on the moon throws a baseball upward. The height of the ball in feet (y) is related to the number of seconds since the ball was thrown (x).
y=-2.7x^2+30x+6.5
A. How high will the ball be after 3 seconds?
B. Give two approximate times (in seconds) that the ball will be at a height of 75 feet.
How many seconds on its way up?
C. How many seconds on its way down?
Please help me solve this! Im stuck, thank you!
Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
-2.7x^2+30x+6.5=y
at 3 seconds
-9(2.7)+90+6.5=72.2 feet.
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-2.7x^2+30x+6.5=75
-2.7x^2+30x-68.5=0
since approximate is desired, graph it.
graph%28300%2C300%2C-3%2C12%2C-10%2C100%2C-2.7x%5E2%2B30x%2B6.5%2C75%29
3 and 8 seconds. We know 3 seconds is approximate from the first, and f(8)=73.7.
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on the way up need the vertex, which has a t value of -b/2a, and that is -30/-5.4 or 5.6 seconds. Same time down.