SOLUTION: When a ball is served, consider the trajectory of ball modelled by equation y=-x^2/8 + 9x/8 +5/4. Find the height of the ball when it is 3m horizontally from where served. (Y repr

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: When a ball is served, consider the trajectory of ball modelled by equation y=-x^2/8 + 9x/8 +5/4. Find the height of the ball when it is 3m horizontally from where served. (Y repr      Log On


   

Question 1028260: When a ball is served, consider the trajectory of ball modelled by equation y=-x^2/8 + 9x/8 +5/4. Find the height of the ball when it is 3m horizontally from where served. (Y represents height of ball in metres above ground and x represents horizontal distance from when ball was struck).
I believe 5/4 (y intercept)represents the initial height and that the ball travels 10m (x intercept) but I'm stuck with how to calculate the height after 3 metres.
any help/advice would be great
Thanks
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
When a ball is served, consider the trajectory of ball modelled by equation y=-x^2/8 + 9x/8 +5/4.
Find the height of the ball when it is 3m horizontally from where served.
(Y represents height of ball in metres above ground and x represents horizontal distance from when ball was struck).
y=-x%5E2%2F8+%2B+%289x%29%2F8+%2B+5%2F4
find y when x=3
y=-3%5E2%2F8+%2B+%289%2A3%29%2F8+%2B+5%2F4
y=-9%2F8+%2B+27%2F8+%2B+5%2F4
y=+18%2F8+%2B+5%2F4
y=+9%2F4+%2B+5%2F4
y=+14%2F4
y = 3.5 meters is the height