The altitude of an object in feet is given by h=-16t^2+8t+48. What is its maximum altitude? After how many seconds 't' will it strike the ground?

Question

anonymous · Answer

ok so what your going to use is the quadratic formula $$-b \pm \sqrt{(b)^{2}-4ac}\div2a$$ so first plug in the equation

anonymous · Answer

after plunging in the equation tell me what you got

ny,ny · Answer

x=-13.61 or x=14.11 approximately.

anonymous · Answer

i am not sure about that can you quickly show your work?

ny,ny · Answer

$$-8\pm \sqrt{-8^{2}-4(-16)(48)}$$

ny,ny · Answer

and then divided by -32

anonymous · Answer

h=-16t^2+8t+48
h=-16t^2+8t-1+1+48
h= 49 - (4t-1)^2 
thus max altitude is 49  when t=1/4

anonymous · Answer

by putting h=0 one can find after how many sec it reache s the ground
thus
49 - (4t-1)^2=0
(4t-1)^2=49

4t-1=+-7
t =(1+-7)/4  

since t cannot be negative 
hence reqd t=(1+7)/4=2

anonymous · Answer

@ NY,NY

check the alternate method shown

ny,ny · Answer

thanks. :)

anonymous · Answer

welcome dear