Question

I need someone who's good at using the quadratic formula

Answer 1

Please post your question.

Answer 2

There @silversurfer

Answer 3

Can you tell under what condition the ball hits the ground ?

Answer 4

h=0

Answer 5

The height has to become zero,right? So, you make h=0 and equate the quadratic part to zero. Then, you just solve for x, in this case, this is the variable t.

Answer 6

The quadratic equation can be rewritten as 5t^2+5t-45=0. Then you can simplify it further by dividing with 5 on both sides, doing which gives you t^2+1-9=0. Now, you can use the quadratic formula given below.

Answer 7

\[t^2 -t-9=0\]

Answer 8

using the quadratic formula:
\[t=\frac{-b \pm \sqrt{b^2 -4ac}}{2a}\]

Answer 9

A correction to my previous equation, it would be t^2+t-9=0. Sorry, it was careless of me.

Answer 10

yes indeed:
t^2 + t - 9 =0 :P

Answer 11

Then use the formula given by sayak to solve for t. Keep in mind, the equation is of the form ax+bx+c=0 where x is t in this case.Hope this helps.

Answer 12

yes but how do i solve for t and find out the seconds?

Answer 13

\[t=\frac{\sqrt{37}-1}{2}\]

Answer 14

a=1,b=1,c=-9, plug in the values in the formula now. I haven't checked but if you get a negative time as one of the roots, you can rule that out.

Answer 15

which should approximately be equal to 2.5

Answer 16

@getoffmyback got it?

Answer 17

yes I'm following

Answer 18

Clearly speaking, there would be two answers. Check for yourself to see which one is reasonable.

Answer 19

yes it gives me an option of just one

Answer 20

@sayakdbz I have to round to the nearest hundredth

Answer 21

nearest hundredth? hm...

Answer 22

That means one of the answers won't be reasonable. Don't be daunted at that, you will understand for yourself once you calculate the two values.

Answer 23

yea @sayakdbz

Answer 24

I already gave the answer needed:
2.5 which is:
t=\frac{sqrt{37}-1}{2}

Answer 25

\[t=\frac{\sqrt{37}-1}{2}\]

Answer 26

rounding 2.5 to the nearest 100th

Answer 27

oh I thought that was the tenth

Answer 28

my bad

Answer 29

wait, sorry :P
i approximated the original answer
rounded off to the nearest 100th the answer is
2.54 seconds

Answer 30

well thank u all for your help @silversurfer @sayakdbz and @isag

Answer 31

@getoffmyback u are most welcome