Quadratic Application

When I want to find the maximum or minimum height of an object, I should_____.

• Set the equation = 0 and solve.
• Use x = (-b/2a) as my answer.
• Substitute x = 0 into the equation.
• Find the y-coordinate for the vertex.

If I want to find out when an object hits the ground, I should _________.

• Use x = (-b/2a) as my answer.
• Set my equation = 0 and solve.
• Replace x with 0 and evaluate.
• Find the y-coordinate of the vertex.

A soccer ball is kicked from the ground with an initial upward velocity of 90 feet per second. The equation h=-16t² + 90t gives the height h of the ball after t seconds.
What is the maximum height of the ball?

• 126.56 ft
• 5.625 sec
• 2.81 sec
• 90 ft

A soccer ball is kicked from the ground with an initial upward velocity of 90 feet per second. The equation h=-16t² + 90t gives the height h of the ball after t seconds.
How many seconds will it take the ball to hit the ground?

• 126.56 ft
• 5.625 sec
• 2.81 sec
• 0 ft

The function f(t) = -5t²+20t + 60 models the approximate height of an object t seconds after it is launched. How many seconds does it take the object to hit the ground?

• 4 seconds

• -2 seconds

• 6 seconds

• 9 seconds

What is the initial (starting) height of an object following this path?  h(t) = -16t² +20t + 6

• -16 feet 
• 0 feet
• 20 feet 
• 6 feet