Question

Ajuggler throws a ball in the air, releasing

it 5 feet above the ground with an initial
velocity of 15 feet per second. She
catches the ball with her other hand when
the ball returns to 5 feet above the
ground. If the equation, y=-16x2 + 15x,
gives the path of the ball from hand to
hand, find how high she throws the ball
(round to the nearest hundredth).

Answer 1

step 1. The vertex is when x = -b/2a (by definition)

step 2. a = -16, b = 15. x(vertex) = -15/2(-16) = 15/32

step 3. y(vertex) = -16(15/32)^2 + 15(15/32) = 225/64 = 3 33/64

step 4. since the ball started at a height of 5 feet you add 5.

step 5. answer: 3 33/64 + 5 = 8 33/64.