Question

A firecracker shoots up from a hill 140 feet high with an initial speed of 100 feet per second. Using the formula H(t) = −16t2 + vt + s, approximately how long will it take the firecracker to hit the ground?

Answer 1

-16t^2+100t+140=0
make sense?

Answer 2

I understand that part it's after that that confuses me

Answer 3

do you know the quadratic formula?

Answer 4

-16t^2 + 100t+140 = 0
-8t^2+50t+70=0
-4t^2+25t+35=0
t^2-25/4t-35/4=0
t^2-25/4t = +35/4
(t-25/8)^2 = 35/4+(25/8)^2
t-25/8 = +-sqrt(35/4+(25/8)^2)
t = +-sqrt(35/4+(25/8)^2)+25/8

Answer 5

Yes, but everytime I solve one of these equations that says " aprroximately how long does this object take to hit the ground" I always mess up. Idk why

Answer 6

this is the method of completing the square. Do you know it?

Answer 7

or solve this
-100+-sqrt(100^2-4(-16)(140))/(2(-16))

Answer 8

No. But when youtry to show me is there any way you could draw it out because you typing it just confuses me even more.

Answer 9

drawing on here is very hard, I cant really draw out equations.

Answer 10

oh sorry I've never tried it

Answer 11

And I did the last equation you put up and got an answer in the hundreds?