Question 1124861
 Benny and Jenny are identical twins.
 They are both the same height. Benny is standing 15 feet away from Jenny.
 He throws a ball to her and the highest height the ball reaches is 10 feet before she catches it.
 Sketch a graph and write an equation that models the path of the ball.
:
{{{ graph( 300, 200, -6, 17, -4, 15, -.178x^2+2.67x, 10) }}}
:
Derived the equation for this graph using the form ax^2 + bx = y
x=15; y=0
225a + 15b = 0
x=7.5; y=10, (axis of symmetry)
56.25a + 7.5b = 10
multiply by 2 and subtract from the 1st equation
225a + 15b = 0
112.5a +15b = 20
-------------------subtraction eliminates b, find a
112.5a + 0 = -20
a = -20/112.5
a = -.178
find b
-.178(225) + 15b = 0
-40 + 15b = 0
15b = 40
b = 40/15
b = 2.67
the equation
y = -.178x^2 + 2.67x; will result in the above graph