Answer:t = 0.268 seconds
t= 3.32 seconds
Find all values of t for which the ball's height is 8 meters.
h = -5t2 + 20t + 3
8 = -5t2 + 20t + 3
Subtract 8 from both sides of the equation
0 = -5t2 + 20t - 5
This is a parabola which opens downward
a = -5
b = 20
c = -5
the vertex -b/2a, h; (2, 23)
-20/2(-5) = -20/-10 = 2
h = -5(22) + 20(2) + 3
h = -20 + 40 + 3 = 23
Use the Quadratic Formula to solve for t
0 = -5t2 + 20t - 5
Dividing both sides of the equation by 5 makes the math easier
0 = -t2 + 4t -1
Now
a = -1
b = 4
c = 1
(-b±(√b2-4ac))/2a
(-4(±√16 - 4))/-2
(-4±(√12))/-2
-4/-2 + 2√3/-2
2 - √3 = 0.26795 seconds
-4/-2 - 2√3/-2
2 + √3 = 3.732 seconds
Step-by-step explanation: