Question

A ball is thrown from a height of 255 feet with an initial downward velocity of 21/fts. The ball's height h (in feet) after t seconds is given by the following.
h=255-21t-16t^2
How long after the ball is thrown does it hit the ground?
Round your answer(s) to the nearest hundredth.

Answer 1

first step:

if the general form of a parabola is

ax^2 + bx + c

and your equation is

255-21t-16t^2

what are your a, b, and c values?

Answer 2

a=16 b=21 and c=225

Answer 3

check your signs

Answer 4

explain?

Answer 5

don't forget to include negative signs if they are present

Answer 6

So a=-16 b=-21 and c=225 ?

Answer 7

good!

now, are you familiar with the quadratic formula?

Answer 8

Wouldnt this be it?

Answer 9

yes that is it

Answer 10

yeah, then you just plug everything into the formula

Answer 11

now, which solution do you think we should pick?

Answer 12

you cant have negative time

Answer 13

It would be the second option.

Answer 14

yes correct

Answer 15

https://www.wolframalpha.com/input/?i=solve+255-21t-16t%5E2