Question 422234
 speed in still water = 	r		
current speed 		2		
				
upstream speed = r-2		
downstream speed = r+2		
				
Distance= 	6 miles		
				
Time upstream + time downstream = 4 hours
t=d/r				

6/(r+2)+	6/(r-2)=	4				
LCD =(r-	2)(r+2)								
6*(r-2)	+6(r+2)=	4				
6r-12+6r	+12=4(r^2-4)
12r=4r^2	-16								
4r^2-12r	-16=0
4(r^2-3r-4)=0	
(r^2-3r-4)=0							
						
Find the roots of the equation by quadratic formula		
a=  1 , b = -3  , c =  -4   .						
b^2-4ac=	25
{{{x1=(-b+-sqrt(b^2-4ac))/(2a)}}}	
{{{x1=(3+sqrt(25))/2}}}
x1=4
{{{x2=(-b+-sqrt(b^2-4ac))/(2a)}}}	
{{{x2=(3-sqrt(25))/2}}}
x2=-1 ( this is negative so not possible)
The speed of paddling in still water = 4 mph