Quadratic Applications

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 fountain shoots water in an arc over a lake that can be modeled by the graph of the equation y= -0.4x² + 8x where x is the horizontal distance (in feet) from the fountain base and y is the height (in feet) above the river.  How high does the water go?

• It goes 11.78 feet high
• It goes 20 feet high
• It goes 40 feet high
• It goes 10 feet high

The length of a rectangle is 6 meters more than the width.  The area is 72 square meters.  Find the length and width.

• Length = 6, Width = 12
• Length = 18, Width = 4
• Length = 12, Width = 6
• Length = 4, Width = 6

A raft is dropped from a helicopter 256 feet in the air above the ocean.  Its approximate height, h, after t seconds is given by the function h(t) = -16t² + 256.  How many seconds did it take the raft to hit the water? 

• -4
• 2
• 4
• 8

An object flies through the air and follows a parabolic path. What does the y-axis represent? 

• time 
• height from the ground 
• horizontal distance 
• money 

An object flies through the air and follows a parabolic path. Which of these typically represents the x-axis? 

• time 
• height from the ground 

If path of a projectile is modeled by: 
h(t) = -16t² + 20t +6, what is the height after 1 second? 

• 6 feet 
• 20 feet 
• 10 feet 
• 4 feet 

If the graph shows price vs profit, what is the maximum profit? 

• 35
• 12,000
• 12,500
• 60

If the graph shows price vs profit, at which prices would you "break even" (neither lose or gain money)? 

• 10 and 60 
• 20 and 50 
• 30 and 40 
• 35