SOLUTION: Lanu hit a volleyball into the air with an initial upward velocity of 24ft per sec. The height H in ft, can be modeled by h= -16t^ + 24t + 3, where t = times in sec. Need to FIND

Algebra ->  Rectangles -> SOLUTION: Lanu hit a volleyball into the air with an initial upward velocity of 24ft per sec. The height H in ft, can be modeled by h= -16t^ + 24t + 3, where t = times in sec. Need to FIND      Log On


   

Question 424882: Lanu hit a volleyball into the air with an initial upward velocity of 24ft per sec. The height H in ft, can be modeled by h= -16t^ + 24t + 3, where t = times in sec. Need to FIND the time it takes the ball to reach 12 feet above ground. Please show work, as I'm having issues with the ^ sq root. THank you so very much
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
Lanu hit a volleyball into the air with an initial upward velocity of 24ft per sec.
The height H in ft, can be modeled by h= -16t^2 + 24t + 3, where t = times in sec.
Need to FIND the time it takes the ball to reach 12 feet above ground.
:
It -16x squared, not square root
:
replace h with 12
-16t^2 + 24t + 3 = 12
-16t^2 + 24t + 3 - 12 = 0
-16t^2 + 24t - 9 = 0
Multiply by -1, change the signs
16t^2 - 24t + 9 = 0
This looks like a perfect square, factors to:
(4t-3)(4t-3) = 0
solution
4t = 3
t = 3%2F4
t = .75 sec to reach 12 ft, (this is also the max height of the ball)
:
Looks like this
+graph%28+300%2C+200%2C+-1%2C+3%2C+-5%2C+15%2C+-16x%5E2%2B24x%2B3%2C+12%29+
Green line represent 12 ft