SOLUTION: A baseball player hits a ball into the air. The ball's height above the ground, in metres, t seconds after being hit, is approximated by h(t)=1+13t-5t^2. Algebraically determine th

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: A baseball player hits a ball into the air. The ball's height above the ground, in metres, t seconds after being hit, is approximated by h(t)=1+13t-5t^2. Algebraically determine th      Log On


   

Question 122238: A baseball player hits a ball into the air. The ball's height above the ground, in metres, t seconds after being hit, is approximated by h(t)=1+13t-5t^2. Algebraically determine the time when the ball first reaches a height of 9 m.
Answer by algebrapro18(249) About Me  (Show Source):
You can put this solution on YOUR website!
well all you have to do here is plug 9 in for h(t) and solve for t.

9 = 1 + 13t -5t^2 ---> Combine like terms
5t^2-13t+8 = 0 ---> factor
(5t-8)(t-1)=0
--->set each factor to zero and solve
5t-8=0 ---> add 8 to both sides
5t = 8 ---> divide both sides by 5
t = 8/5

t-1 = 0 --> add 1 to both sides
t = 1

so the ball reaches the height of 9 meters 1 second after it was hit.