Question

A ball is thrown from a height of 156
feet with an initial downward velocity of
8/fts. The ball's height h (in feet) after
t seconds is given by the following.
h=156−8t-6t^2
How long after the ball is thrown does it hit the ground?

Answer 1

@Directrix

Answer 2

h=156−8t-6t^2

0 = 156−8t-6t^2

Answer 3

@Directrix can't you solve it using quadratic formula?

Answer 4

I'm trying to decide if the 0 is in the right place.

Answer 5

4.47
-5.80
before i round up

Answer 6

i used quadrtic formula

Answer 7

\[a x^{2}+bx+c=0\]
So a would be 6
b would be 8
c would be -156

And quadratic formula would be \[\frac{ -b \pm \sqrt{b ^{2}-ac} }{ 2a }\]
Then plug and chug

Answer 8

I would set it to 0

Answer 9

Let me see what I get. I think that the zero is in the right place.

Answer 10

i havent inputted yet i wait for u to tell me if im right

Answer 11

>>4.47 -5.80

I got these but which one is the answer? And what about the rounding?

Answer 12

i have a button for or so i have to put both

Answer 13

4.48
-5.81 ??

Answer 14

Okay. Any instructions about rounding?

Answer 15

Round at the very end

Answer 16

nearest hundreth

Answer 17

I also get 4.48

Answer 18

Wait a minute.

Answer 19

im waiting

Answer 20

-5.81 and 4.48 @jaeuni Did you get that?

Answer 21

i did

Answer 22

Yep

Answer 23

incorrect

Answer 24

Oh, no.

Answer 25

Any comments given about the answer?

Answer 26

no just incorrect

Answer 27

Do you have another shot or is this it?

Answer 28

Did you type in both -5.81 and 4.48?

Answer 29

one more

Answer 30

yes

Answer 31

Let me see who is online and might know what's wrong with this problem's solution.

Answer 32

it gives me 2 chances if i get first wrong it makes e do another question

Answer 33

Isn't it just the positive value since you can't have negative seconds in real life scenarios?

Answer 34

all the others accepted the neg

Answer 35

Interesting...

Answer 36

thats what i thought

Answer 37

it booted me out and gave the answer 2.88

Answer 38

Correct. No negative time :)
4.48 should have been accepted D:
2.88? weirddddd

Answer 39

Thanks. @zepdrix