Question

Please Help!!!!!!!!!!!!!!!!!!!!!

Answer 1

5. You live near a bridge that goes over a river. The underside of the bridge is an arch that can be modeled with the function y = –0.000475x2 + 0.851x, where x and y are in feet. How high above the river is the bridge (the top of the arch)? How long is the section of bridge above the arch? (1 point)
The bridge is about 1,791.58 ft. above the river, and the length of the bridge above the arch is about 381.16 ft.
The bridge is about 1,791.58 ft. above the river, and the length of the bridge above the arch is about 895.79 ft.
The bridge is about 381.16 ft. above the river, and the length of the bridge above the arch is about 895.79 ft.
The bridge is about 381.16 ft. above the river, and the length of the bridge above the arch is about 1,791.58 ft.

Answer 2

A: The second answer.
Why? I cheated.
http://www.wolframalpha.com/input/?i=y+%3D+%E2%80%930.000475x2+%2B+0.851x

Answer 3

jc.croft1: cheater!

The x-coordinate of the vertex of a parabola is -b/2a
a=-0.000475, b=0.851
Substitute in the x-coordinate to find the y-coordinate, which is the height of the bridge.

The length of the bridge is the distance between the two zeroes. The first zero is obvious (x=0) but you have to use the quadratic formula to find the second one!

Answer 4

Can you guys help with another @BluFoot and @jc.croft1

Answer 5

go ahead :)

Answer 6

Sure.

Answer 7

The graph below models the acceleration of a car. Interpret the meaning of the vertex.
The car traveled 10 miles in 60 seconds.
It took the car 20 seconds to accelerate.
It took the car 10 seconds to reach a speed of 60 miles per hour.
It took the car 20 seconds to reach a speed of 60 miles per hour.

Answer 8

The third option. @BluFoot ?
It reaches the peak at time = 10 and speed = 60.

Answer 9

thats right

Answer 10

Let's look at them one at a time:
a) obviously wrong since the graph only goes to 20 seconds
b) it's decelerating at 10 seconds so that's wrong
c) at 10 seconds, it's going 60 mph so that seems good
d) at 20 seconds it's going 0mph that's wrong

Answer 11

1. What is the equation, in standard form, of a parabola that contains the following points?

(–2, 18), (0, 2), (4, 42)

(1 point)
y = –2x2 – 2x – 3
y = –3x2 + 2x – 2
y = 3x2 – 2x + 2
y = –2x2 + 3x + 2

Answer 12

This is a lot harder. The easiest way is just to plug in the points into the equations and see if they work. For example, if you plug in (0,2) into the first equation

2=-2(0)^2-2(0)-3
2=-3

obviously that doesn't work so it's not the first equation

If they hadn't given you the answers you'd have to do it the long way.

http://www.algebra.com/algebra/homework/quadratic/Quadratic_Equations.faq.question.1829.html

Answer 13

I agree, just sub in the values and see which equation works.