SOLUTION: A parabola shaped tunnel is 10m high at the centre and spans 18m wide at the base. A 7.5 m high vehicle needs to use the tunnel;, what is the maximum width of the vehicle that can

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Question 750248: A parabola shaped tunnel is 10m high at the centre and spans 18m wide at the base. A 7.5 m high vehicle needs to use the tunnel;, what is the maximum width of the vehicle that can fit through the tunnel?
I need to draw a diagram to represent the tunnel on a coordinate number plane , and find the equation of the parabola. using algebra and coordinate geometry to determinate the maximum width of the truck
I try to solve this problem many times but my results seems to be wrong, please help me I'm so stuck
Ally

Answer by josmiceli(19441)   (Show Source): You can put this solution on YOUR website!
Think of this as a parabola that opens downward, and
the base, or the road, is the x-axis. The y-axis goes
through the maximum height. The x-intercepts are at
( 9,0 ) and ( -9,0 ), making the base 18 wide
-------------------
The vertex of the parabola is at ( 0,10 )
Find the equation of the parabola
It will have the general form

The x-coordinate of the vertex is at
I have stated that


So far, I have


-----------------
Also, the vertex is at ( 0,10 ), so I can say

, and so far I have

------------------
The other points I have are ( -9,0 ) and ( 9,0 )
If I say

If or , then



---------------
The whole equation is:

------------------------
Here's the plot:

-------------------------
What they want to know is:
What is when , and
What is when
Then you find , which is the width of the truck.
-----------------------







The maximum width of the truck is 9 m
---------------
check:







OK



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