Question

A firecracker shoots up from a hill 145 feet high with an initial speed of 80 feet per second. Using the formula H(t) = −16t^2 + vt + s, approximately how long will it take the firecracker to hit the ground?

Answer 1

i'll just put down the same method.. but you'll need to plug in different values for v and s into your quadratic..
http://openstudy.com/study#/updates/50119db9e4b08ffc0ef3d552

Answer 2

i understand the formula but how do you solve for t?

Answer 3

do you know how to use the quadratic formula?

Answer 4

not really

Answer 5

yes i know what it is but not good using it

Answer 6

the solution to the quadratic equation: \(\large ax^2+bx+c=0 \)
is obtained by the quadratic formula: \(\large x=\frac{-b\pm\sqrt{b^2-4ac}}{2a} \)

Answer 7

first you need to identify your a, b, c:
a =
b =
c =

can you give me those values?

Answer 8

a is 16 b is 145 and c is 80

Answer 9

no.. be careful... a=-16
but there's more....

Answer 10

thought i put the - my bad

Answer 11

in the equation H(t) = −16t^2 + vt + s,
v represents your initial velocity
s represents your initial height

Answer 12

so v is 80 and s is 145

Answer 13

yes....
so
a =
b =
c =
???

Answer 14

a is -16 b is 80 c is 145

Answer 15

yes....
now all you need to do is to stick these values into the quadratic formula.... let your calculator do the rest....

Answer 16

ok thanks

Answer 17

\[\huge x=\frac{-(80)\pm\sqrt{80^2-4(-16)(145)}}{2(-16)} \]

Answer 18

yw...:)

Answer 19

i forgot... the quadratic formula will give you two solutions.... choose the one that makes sense....

Answer 20

ok