Question 539707
Boat speed		x   		
current speed 		5		
				
against current x-		5	kph	
with current x+		5	kph	
				
Distance= 	3	km		
				
Time against + time with  = 			10	hours
t=d/r				

3	/(	x   	+	5	)	+	3	/(x	-	5	)	=	10				
																	
LCD =	(x	-	5	)	(	x   	+	5	)								
3	*(	x   	-	5	)	+	3	(x	+	5	)	=	10				
3	x   	-	15	+	3	x   	+	15		=	10	(	x ^2		-	25	)
6	x   	=	10	x ^2	-	250											
10	x ^2	-	-6	x   	-	250											
																	
Find the roots of the equation by quadratic formula																	
																	
a=	10	,	b=	-6	,	c=	-250										
																	
b^2-4ac=	36	+	10000														
b^2-4ac=	10036		{{{	sqrt(	10036	)=	100.18	}}}									
{{{x=(-b+-sqrt(b^2-4ac))/(2a)}}}																	
{{{x1=(-b+sqrt(b^2-4ac))/(2a)}}}																	
x1=(	6	+	100.18	)/	20												
x1=	5.31																
x2=(	6	-100.18	) /	20													
x2= 	-4.71																
Ignore negative value		
Boat speed = 5.31 mph	

ma.ananth@hotmail.ca