Question 937920
boat   	speed	x   	km 		Time forward + time return = hours		
current     	speed	3	km 				
							
against	current     	x-	3	km/h			
with	current     	x+	3	km/h			
							
Distance=	14	km 					
							
Time against + time with  =			2.5	hours			
t=d/r							
							
14	/(	x   	+	3	)	+	14
							
LCD =	(x	-	3	)	(	x   	+
14	*(	x   	-	3	)	+	14
14	x   	-	-42	+	14	x   	+
28	x   	=	2.5	x ^2		-22.5	
2.5	x ^2	-	-28	x   	-	-22.5	=
							
Find the roots of the equation by quadratic formula							
							
a=	2.5	,	b=	-28	,	c=	-22.5
							
b^2-4ac=	784	+	225				
b^2-4ac=	1009						
{{{	sqrt(	1009	)=	31.76	}}}		
{{{x=(-b+-sqrt(b^2-4ac))/(2a)}}}							
{{{x1=(-b+sqrt(b^2-4ac))/(2a)}}}							
x1=(	28	+	31.76	)/	5		
x1=	11.95						
{{{x2=(-b-sqrt(b^2-4ac))/(2a)}}}							
x2=(	28	-31.76	) /	5			
x2=	-0.75						
Ignore negative value							
boat   	speed	11.953	km/h	

Time upstream = 	(14/8.953)*60		=94 minutes
							
m.ananth@hotmail.ca