Question 415647
speed	x					
speed	x+50 after one year			
						
Distance = same	400km			
original time – time with increased speed =1hour
t=d/t						
400/x-400/(x+400	)=1				
LCD= (x+	400)	
multiply by LCD																
400(x+400)-400x	=x(x+400	)
400x+160000-400x	=1X^2+400x				
160000=X^2+400x							
X^2+400x-160000	=0
solve using quadratic formula

a= 1  , b = 400  , c ==-160000     .

b^2-4ac=800000

{{{x=(-b+-sqrt(b^2-4ac))/(2a)}}}


{{{x1=(-400+sqrt(800000))/(2)}}}
x1= 247.21 
x2 is negative so ignore
original speed = 247.21 mph
after one year speed= 297.21 mph

...
{{{x2=(-b-sqrt(b^2-4ac))/(2a)}}}