Question 475858
first part	60	miles													
second part	75	miles													
															
speed in first part	x			mph											
speed second part	x		-5	mph											
Total rowing time		8	hours												
Time first part		60	/	x											
Time second part		75	/	(	x	-5	)								
															
Time first part + time second part =	8	hours											
															
60/x +	75/(x-5)=	8			
LCD =	x*	(x	-5	)							
multiply the equation by the LCD															
we get															
60*((x-5)+75	x=	8			
60x-300	+75x=8x^2-40	x
175x-300=8X^2										
8	X^2	-175	x	300			=	0							
8	X^2+	-175	x+	300	=										
/	8														
1	X^2	-21.88	x	37.5	=										
															
Find the roots of the equation by quadratic formula															
															
a=	1	b=	-21.88	c=	37.5										
															
b^2-4ac=	478.52	-	-150												
b^2-4ac=	328.52			
{{{sqrt(	328.52	)}}}=	18.13								
{{{x=(-b+-sqrt(b^2-4ac))/(2a)}}}															
{{{x1=(-b+sqrt(b^2-4ac))/(2a)}}}															
x1=(	21.88	+	18.13	)/	2										
x1=	20		20    					L=						90	20
x2=(	21.88	-18.13	) /	2											
x2= 	1.88		1 7/8												
Ignore x2															
x	=	20	mph																
CHECK															
Time first part	+	Time second part													
3	+	5	=	8	

m.ananth@hotmail.ca