a rock falls from a tower that is 432 feet high. as it is falling, its height is given by the formula h=432-16ft^2. how man secods will it take for the rock to hit the ground (h=0)

Question

a rock falls from a tower that is 432 feet high.  as it is falling, its height is given by the formula h=432-16ft^2. how man secods will it take for the rock to hit the ground (h=0)

anonymous · Answer

you mean?
$$h=432-16t^2$$

anonymous · Answer

yes

anonymous · Answer

typo

anonymous · Answer

put 0 instead h (as it said) and solve quadratic equation

anonymous · Answer

20.4

anonymous · Answer

no

anonymous · Answer

how you got 20.4?

anonymous · Answer

mental math

anonymous · Answer

then do it on paper and you will get correct answer :D

anonymous · Answer

didn't serve me so well

lalaly · Answer

0 = 432 - 16t²
0 = 16(27 - t²)
27 - t² = 0
-t² = -27
t² = 27
t = 3√3

anonymous · Answer

oh you don't need to do that because you got answer :/

anonymous · Answer

not technically. i needed 5.2 seconds

anonymous · Answer

y^2=18



9 correct?

anonymous · Answer

i think you should write it precisely 3sqrt3 unless told otherwise

anonymous · Answer

no, 9*9=81

anonymous · Answer

was told otherwise, to write in seconds.

anonymous · Answer

you can easily write $3\sqrt3$ second

anonymous · Answer

ya, 5.2

anonymous · Answer

$$\sqrt{18}=\sqrt{2\cdot9}=3\sqrt2$$

anonymous · Answer

well write how you want, idk how you are being taught in your country

anonymous · Answer

another problem i can't figure is y^2=18

anonymous · Answer

not very well, i am 24 and don't get this junk

anonymous · Answer

$$\sqrt{18}=\sqrt{2\cdot9}=3\sqrt2$$

anonymous · Answer

not an answer

anonymous · Answer

then your answers are incorrect

anonymous · Answer

http://www.wolframalpha.com/input/?i=sqrt18

anonymous · Answer

324, +,- sqrt18, 9, or sqrt18

anonymous · Answer

i did, doesn't work either