Question 803333
boat   	speed	x   	kph														
current     	speed	4	kph														
																	
against	current     	x-	4	kph													
with	current     	x+	4	kph													
																	
Distance=	1	miles															
																	
Time against + time with  =			5	hours													
t=d/r																	
																	
1	/(	x   	+	4	)	+	1	/(x	-	4	)	=	5				
																	
LCD =	(x	-	4	)	(	x   	+	4	)								
1	*(	x   	-	4	)	+	1	(x	+	4	)	=	5	(x^2	-	16	)
1	x   	-	-4	+	1	x   	+	4		=	5	(	x ^2		-	16	)
2	x   	=	5	x ^2		-80											
5	x ^2	-	-2	x   	-	80											
																	
Find the roots of the equation by quadratic formula																
																	
a=	5	,	b=	-2	,	c=	-80										
																	
b^2-4ac=	4	+	1600														
b^2-4ac=	1604																
{{{	sqrt(	1604	)=	40.05	}}}												
{{{x=(-b+-sqrt(b^2-4ac))/(2a)}}}																	
{{{x1=(-b+sqrt(b^2-4ac))/(2a)}}}																	
x1=(	2	+	40.05	)/	10												
x1=	4.20																
{{{x2=(-b-sqrt(b^2-4ac))/(2a)}}}																	
x2=(	2	-40.05	) /	10													
x2=	-3.80																
Ignore negative value																	
boat   	speed	4.205	kph														
																	
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