SOLUTION: The equation h=-16t^2-32t+320 Give the height of a ball, thrown donward from top of a 320ft. Building with an initial velocity of 32ft/s. Find the time it takes for the ball to

Algebra ->  Customizable Word Problem Solvers  -> Misc -> SOLUTION: The equation h=-16t^2-32t+320 Give the height of a ball, thrown donward from top of a 320ft. Building with an initial velocity of 32ft/s. Find the time it takes for the ball to       Log On

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Question 124439: The equation h=-16t^2-32t+320
Give the height of a ball, thrown donward from top of a 320ft. Building with an initial velocity of 32ft/s. Find the time it takes for the ball to reach a height of 64ft.
Answer by checkley71(8403) About Me  (Show Source):
You can put this solution on YOUR website!
H=-16T^2-32T+320
64=-16T^2-32T+320
-16T^2-32T+320-64=0
-16T^2-32T+256=0
-16(T^2+2T-16)=0
USING THE QUADRATIC EQUATION:x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
X=(-2+-SQRT[2^2-4*1*-16])/2*1
X=(-2+-SQRT[4+64])/2
X=(-2+-SQRT68)/2
X=(-2+-8.246)/2
X=(-2+8.246)/2
X=6.246/2
X=3.123 SECONDS. ANSWER FOR THE TIME FOR THE BALL TO BE @ 64 FT FROM THE GROUND.