SOLUTION: A soccer ball is kicked in the air from the stadium. The height, h, in feet, of the ball can be modeled by the equation h = -16t2 + 34t + 15 where t is the time in seconds. When wi

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: A soccer ball is kicked in the air from the stadium. The height, h, in feet, of the ball can be modeled by the equation h = -16t2 + 34t + 15 where t is the time in seconds. When wi      Log On


   

Question 1181972: A soccer ball is kicked in the air from the stadium. The height, h, in feet, of the ball can be modeled by the equation h = -16t2 + 34t + 15 where t is the time in seconds. When will the ball hit the ground?
Found 2 solutions by Boreal, MathLover1:
Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
h(t)=-16t^2+34t+15
set it equal to 0, the ground.
may rewrite as
16t^2-34t-15=0, multiplying by -1
t=(1/32)(34+/-sqrt(2116))
=(1/32)(80), only positive root of 2.5 seconds.
graph%28300%2C300%2C-5%2C5%2C-10%2C35%2C-16x%5E2%2B34x%2B15%29

Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

h+=+-16t%5E2+%2B+34t+%2B+15++

the ball will hit the ground when h=0
0=+-16t%5E2+%2B+34t+%2B+15++....factor
0=+-%2816t%5E2+-34t+-+15%29++
0=+-%2816t%5E2+%2B6t-40t+-+15%29++
0=+-%28%2816t%5E2+%2B6t%29-%2840t%2B15%29%29++
0=+-%282t%288t+%2B3%29-5%288t%2B3%29%29++
0+=+-%282t+-+5%29+%288t+%2B+3%29+
solutions:
if 0+=+-%282t+-+5%29++=>2t+=5++=>t+=2.5++
if 0+=++8t+%2B+3+=>+8t=-3+=>+t=-3%2F8+-> disregard negative time
the ball will hit the ground after 2.5++ seconds