Question

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If an object is dropped from a height of 200 feet, the function h(t)=-16t^2+200 gives the height of the object after t seconds. Approximately, when will the object hit the ground.

Answer 1

when the object hit the ground, its height will be equal to 0
thus h(t) = 0

so we have to solve -16t^2 + 200 = 0

do you know how to solve it ?

Answer 2

Not exactly, I do know that we need to square 16 and 200 but thats it.

Answer 3

you have two methods here
you either use the quadratic formula

or you can use the identity

a^2 - b^2 = (a-b)(a+b)

Answer 4

you want to use the second method ?

Answer 5

I know the quadratic function very well.

Answer 6

the quadratic equation has the form

ax^2 + bx + c

so the number multiplying x^2 is a
so the number multiplying x is b
so the last number is c

Answer 7

what is multiplying x^2 here ?

Answer 8

-16

Answer 9

correct

what's multiplying x ?

Answer 10

200?

Answer 11

is there any x in the equation ?

Answer 12

-16t^2+200, no

Answer 13

when you don't see x in the equation, it can be written like this

-16x^2 +0x + 200

thus b=0

Answer 14

Ohhh right, I understand.

Answer 15

so can you apply the quadratic formula now ?

Answer 16

184.00 seconds?

Answer 17

can you show me your calculation ?

Answer 18

-16(1)^2+0(1)+200?

Answer 19

what's this ?

Answer 20

do you know the quadratic formula ?

Answer 21

\[\frac{ -b \pm \sqrt{b^2 - 4ac} }{ 2a }\]

Answer 22

Yes I know that

Answer 23

apply it

Answer 24

Our B is 0 correct?

Answer 25

yes

Answer 26

so x= -0+-sq0^2-4*-16*200/2*-16

Answer 27

3.54 seconds

Answer 28

correct

Answer 29

Your a good person for sticking with me! :)

Answer 30

Thanks -_-

Answer 31

glad to help :)