SOLUTION: The following function gives the height, (h) meters, of a batted baseball as a function of the time, t seconds, since the ball was hit. h=-6(t-2.5)^2+38.5 How many seconds after

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: The following function gives the height, (h) meters, of a batted baseball as a function of the time, t seconds, since the ball was hit. h=-6(t-2.5)^2+38.5 How many seconds after       Log On


   

Question 275891: The following function gives the height, (h) meters, of a batted baseball as a function of the time, t seconds, since the ball was hit.
h=-6(t-2.5)^2+38.5
How many seconds after it was hit did the ball hit the ground, to the nearest second?
------------------------------------
I have made an equation of 0=-6(t-2.5)^2+38.5 and then simplified it out to 0=-6t^2+30t+1 but don't know how to solve for t. i have looked at step by step calculators on a bunch of different sites but all of the instructions involved things that i have not learned yet. The answer in the back of the book is 5 and that's what all of the calculators say but i don't know how to get that answer. I just wanted to know if there is an easier way to solve this equation than the calculators give me. Thanks.
Answer by scott8148(6628) About Me  (Show Source):
You can put this solution on YOUR website!
start with the equation you made

subtracting 38.5 ___ -38.5 = -6(t - 2.5)^2

dividing by -6 ___ 6.417 = (t - 2.5)^2

taking square root ___ ±2.533 = t - 2.5 ___ remember square roots can be positive or negative

adding 2.5 ___ 5.033 = t ___ AND ___ -.033 = t

5 is the answer you are looking for

but the -.033 isn't just junk
___ it represents the time that the ball would have STARTED from the ground