Unit rate is miles per 1 gallon
50mi/2 and 1/2 gallon
50mi/2.5 gallon
times 10/10
500mi/25 gallon
20mi/1gallon
answer is 20mi/gal
        
             
        
        
        
The sketch of the parabola is attached below
We have the focus 

The point 

The directrix, c at 

The steps to find the equation of the parabola are as follows
Step 1
Find the distance between the focus and the point P using Pythagoras. We have two coordinates; 

 and 

. 
We need the vertical and horizontal distances to find the hypotenuse (the diagram is shown in the second diagram).
The distance between the focus and point P is given by

Step 2
Find the distance between the point P to the directrix 

. It is a vertical distance between y and c, expressed as 

Step 3
The equation of parabola is then given as 

=


 ⇒ substituting a, b and c


⇒Rearranging and making 

 the subject gives
 
 
        
        
        
Step-by-step explanation:
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