Question 518908
original time - time after speed increase =1

t=d/r

d=210
r=x
210/x -210/(x+5)=1

multiply by the LCD x(x+5)

210(x+5)-240x=x(x+5)
210x+1050-210x=x^2+5x

x^2+5x-1050=0

Find the roots of the equation by quadratic formula								
								
a=	1	,	b=	5	,	c=	-1050	
								
b^2-4ac=	25	+	4200					
b^2-4ac=	4225		{{{	sqrt(	4225	)=	65	}}}
{{{x=(-b+-sqrt(b^2-4ac))/(2a)}}}								
{{{x1=(-b+sqrt(b^2-4ac))/(2a)}}}								
x1=(	-5	+	65	)/	2			
x1=	30							
x2=(	-5	-65	) /	2				
x2= 	-35							
Ignore negative value								
speed = 30 mph

m.ananth@hotmail.ca